During strenuous work a human body generates about 2,400 btus of body heat per hour. if 6 football players are in a gym that is 12 ft × 18 ft × 10 ft lifting weights, how many btus per cubic foot do they produce in 2 hours? (to the nearest tenth)

a) 13.3 btus/ft^3
b) 40.0 btus/ft^3
c) 66.7 btus/ft^3
d) 133.3 btus/ft^3