Answer:
I think its 900 square feet
Explanation:
SA formula for triangular prism
SA=p×H+2B
p is perimeter
h is height
B is area of the base (Base times height)
perimeter is 9+12+15 which is 36
height is 20
area of one of the base is 108
now plug it in and calculate
36×20+2(108)
this is 936
you round down to 900 obviously
and there you go