Given a specific amount of money on hand, calculate the CC bills to pay off to save the most amount of money a month

gistfile1.txt

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace budget {
   public class Program {
        static void Main(string[] args) {
            var debt = new DebtCalculation(500);
            debt.RunBudget();

            Console.ReadKey();
        }
    }

    public class DebtCalculation {
        public DebtCalculation(decimal amountOnHand) {
            // Add as many items that you want
            _budgetItems.Add(new BudgetItem { Name = "Credit Card Name", MonthlyCost = 2, TotalRemaining = 100 });
            _budgetItems.Add(new BudgetItem { Name = "toys R Us", MonthlyCost = 25, TotalRemaining = 1000 });
            _budgetItems.Add(new BudgetItem { Name = "Bank of America", MonthlyCost = 278, TotalRemaining = 2500 });
            _budgetItems.Add(new BudgetItem { Name = "First Bank", MonthlyCost = 23, TotalRemaining = 100 });

            _amountOnHand = amountOnHand;
        }

        private List<BudgetItem> _budgetItems = new List<BudgetItem>();
        private decimal _amountOnHand = 0;

        public void RunBudget() {
            decimal greatestSavings = 0;
            foreach (BudgetItem[] permutation in Permutation.GetPermutations(_budgetItems.ToArray(), _amountOnHand)) {
                decimal amountTotal = 0;
                decimal amountOwed = 0;

                permutation.ToList().ForEach(x => {
                    if (x != null) {
                        amountTotal += x.MonthlyCost;
                        amountOwed += x.TotalRemaining;
                    }
                });

                if (greatestSavings < amountTotal) {
                    List<string> names = new List<string>();

                    permutation.ToList().ForEach(x => {
                        if (x != null) {
                            names.Add(x.Name);
                        }
                    });

                    Console.WriteLine(String.Join(", ", names));
                    Console.WriteLine(amountTotal + " " + amountOwed);
                    greatestSavings = amountTotal;
                }
            }

            //for (int i = 0; i < _budgetItems.Count; i++) {
            //    var totalCalculated = 0;

            //    GetP
            //}
        }
    }

    public class BudgetItem {
        public string Name { get; set; }
        public decimal MonthlyCost { get; set; }
        public decimal TotalRemaining { get; set; }
    }

    public class Permutation {
        public static IEnumerable<BudgetItem[]> GetPermutations(BudgetItem[] items, decimal amountOnHand) {
            int[] work = new int[items.Length];
            for (int i = 0; i < work.Length; i++) {
                work[i] = i;
            }
            foreach (int[] index in GetIntPermutations(work, 0, work.Length)) {
                BudgetItem[] result = new BudgetItem[index.Length];
                var count = 0;
                for (int i = 0; i < index.Length; i++) {
                    if (count == 0) {
                        result[count] = items[index[i]];
                        count++;
                        continue;
                    }
                    decimal amountTotal = 0;

                    result.ToList().ForEach(x => {
                        if (x != null) {
                            amountTotal += x.TotalRemaining;
                        }
                    });

                    if (amountTotal + items[index[i]].TotalRemaining < amountOnHand) {
                        result[count] = items[index[i]];
                        count++;
                    } 
                }
                yield return result;
            }
        }

        public static IEnumerable<int[]> GetIntPermutations(int[] index, int offset, int len) {
            if (len == 1) {
                yield return index;
            }
            else if (len == 2) {
                yield return index;
                Swap(index, offset, offset + 1);
                yield return index;
                Swap(index, offset, offset + 1);
            }
            else {
                foreach (int[] result in GetIntPermutations(index, offset + 1, len - 1)) {
                    yield return result;
                }
                for (int i = 1; i < len; i++) {
                    Swap(index, offset, offset + i);
                    foreach (int[] result in GetIntPermutations(index, offset + 1, len - 1)) {
                        yield return result;
                    }
                    Swap(index, offset, offset + i);
                }
            }
        }

        private static void Swap(int[] index, int offset1, int offset2) {
            int temp = index[offset1];
            index[offset1] = index[offset2];
            index[offset2] = temp;
        }

    }
}