I need help. there are multiple answers. it says which modem can represent the expression ​

we know that

surface area=2*area of the base+perimeter of base*height 

area of the base=b*h/2

b=8 ft

h=15 ft

so

area of triangle=8*15/2> 60 ft²

perimeter of base=a+b+c

a=15 ft

b=8 ft

c=?

applying the Pythagoras theorem

c²=a²+b²> c²=15²+8²> c²=225+64> 289

c=√289> c=17 ft

perimeter=15+8+17=40 ft

height of the prism=20 ft

surface area=2*60+40*20> 920 ft²

the answer is the option

B. 920 ft 2