It’s asking for LATERAL surface area btw

Lateral surface area = 826.5 m²

Step-by-step explanation:

Formula to calculate the lateral surface area of the triangular prism,

Lateral surface area of the triangular prism = Perimeter of the triangular base × Height

Perimeter of the triangular base = 6 + 11 + 12

                                                      = 29 m²

Height of the prism = 28.5 m

Therefore, lateral surface area of the prism = 29 × 28.5

                                                                        = 826.5 m²