I solved the problem using an approach similar to Bunuel's. However, it took me 2:31 min to read the question and solve the problem. I wonder if there is a faster way to solve this problem because these additional seconds (~31 seconds) all add up.
F + 20 * V = 120 * 20
F + 25 * V = 110 * 25
5 * V = 50 (55 - 12 * 4)
5 * V = 50 * 7
V = 70
F = 2400 - 1400 = 1000
Total = 1000 + 70 * 40 = 3800
At this time I looked at the answer choice and did not see anything matching
and quickly realized I need per head cost
So I divided the above result by 40 to get 95.
I could potentially save few seconds if I am more alert but I still feel the above steps would take me 2 min or more.
I would like to know how much time other people are taking to solve the same problem