Answer:
3.45 sqft
Explanation:
Calculate all the areas individually, the 3 lateral sides are the same and using the formula for area we have 1/2 base times height. The height is 2 ft and the base is 1 ft so the area of one of the lateral sides is 1 ft.
There are three lateral sides so you multiply 1 by 3 to get 3.
The base is done the same way. It's base is 1 ft and it's height is 0.9ft so the area is 0.45.
3 + 0.45 = 3.45
The surface area is 3.45 sqft.
I could be wrong but the formula and process is the same, calculate the sides individually using the base height formula for area.