The surface area of the triangular prism is 344ft²
The surface area of prism is generally expressed as ;
SA = 2B + ph
where h is the height , p is the perimeter of the base and B is the base area
Base area = 1/2bh
= 1/2 × 7 × 5
= 17.5ft²
perimeter of the base = 7 + 5 + 8.6
= 20.6 ft
height = 15ft
SA = 2 × 17.5 + 20.6 × 15
= 35 + 309
= 344 ft²
Therefore, the surface area of the prism is 344ft²