Verified Answer :

Find the area of two sides (LengthHeight)2 sides.          12m x 9m
Find the area of adjacent sides (WidthHeight)2 sides.     5m x 9m
Find the area of ends (LengthWidth)2 ends.                     12m x 5m
Add the three areas together to find the surface area.        

The answer is a, 426m^2. the formula to get this is 2(lw+lh+wh) so you input the numbers- 2(12x5 + 12x9 + 5x9)