Minimize shadows placing light sources on a diagram of a room

I’m a CS student and came upon this problem:

Given a diagram of a room with obstacles in it (like walls or furniture), find the 4 best places to put light sources in it so the room has the most light possible, or you can think of, minimizing the amount of shadow in the room.

In other words, if you have 4 sources of light, which are the best places to put them so your room has maximum light (or minimum shadow).

I’ll append an example of a diagram so the problem can be better understood: example of a diagram

The solution I thought was to find the spot with most light and from there find the second one and so on. But something makes me think that it may exist a configuration which is better that doesn’t need to be the best from the beginning, kinda feels like a special case of the knapsack problem, if so I’d think of implementing a greedy algorithm or using genetic algorithms to give an approximation of the best places.

I’m not sure if it’s a math or a CS problem. I’d be grateful if at least someone points me in the right direction so I can do a better research, thank you very much!