gistfile1.txt

var ITEMS = [
  {price: 250},
	{price: 200},
	{price: 150}
];

var SET_PRICE = 550;

function minCountItem(items){
	
	var ret = items[0]
	for(var i = 1; i < items.length; ++i){
		ret = Math.min(ret, items[i]);
	}
	return ret;
}

//console.log(minCountItem([3,3,4]));


/**
 * @params items [ハンバーガーの個数、ポテトの個数、ドリンクの個数]
 */
function buy(items){
	
	var minCount = minCountItem(items);	
	var totalPrice = SET_PRICE * minCount;

	var itemCount;
	for(var i = 0; i < ITEMS.length; ++i){
		itemCount = items[i] - minCount;
		totalPrice += ITEMS[i].price * itemCount;
	}

	return totalPrice;
}

console.log(buy([1,1,1]));
console.log(buy([2,1,1]));
console.log(buy([3,3,1]));