Gold mining problem

gold_mining_problem.txt

You manage a gold mining facility, to simplify mining, lets say each mine has multiple levels that gives you different profit.
For example, you may have 4 gold mines, let's call them a, b, c, d.
Each of them has a couple levels:
a: 1 level
b: 2 levels
c: 1 level
d: 4 levels
and each level have gives you different profit if you mine it:
a: 2
b: 8, 4
c: 6
d: 3, 4, 4, 4
To mine each level, you need a miner, for each extra level you want to reach, you need one extra miner.
Alternatively, there's a technique called explosive mining. You can finish up a single mine with only one miner, but with a profit less than the sum of all levels, greater than the first level, for example:
a: 2
b: 9
c: 6
d: 5
You want to know the maximu profit you can gain given a number of miners.

Exampls:
If you have 1 miner, you should do explosive mining in mine b to gain profit 9
If you have 2 miner, explosive mine b, and normal mine c, to gain profit 9 + 6 = 15
3 miners: explosive mine b and d, normal mine c, you have 9 + 6 + 5 = 20
4 miners: normal mine b 2 levels, normal mine c, explosive mine d, you have 8 + 4 + 6 + 5 = 23
5 miners: explosive mine b, normal mine c, normal mine d 3 levels, you have 9 + 6 + 3 + 4 + 4 = 26

example input of above example:
{"a": {"explosive": 2,
      "normal": [2]},
 "b": {"explosive": 9,
       "normal": [8, 4]},
 "c": {"explosive": 6,
       "normal": [6]},
 "d": {"explosive": 5,
       "normal": [3, 4, 4, 4]}
}