ooh a challenge!
so first find the surface area which is
(2 times legnth times width)+(2 times legnth times height)+(2 times width times height)=(2 times 12 times 10)+(2 times 12 times 16)+(2 times 10 times 16)=(2 times 120)+(2 times 192)+(2 times 160)=240+384+320=944 ft^2
then subtract the area of the door which is 3 times 8=24
so 944-24=920 ft^2
1 quart of paint =100
944/100=9.44
round up because you cant buy a fraction of a bucket but you still need to cover the whole room (minus the door)
10 quarts of paint is the answer