The easiest way to solve this problem is by calculating the areas of all the sides and adding them together.
Step 1; Calculate the area of the rectangular front & back
A = 2 * (l * w)
= 2 * (25 * 10)
Step 2; Calculate the area of the rectangular sides
A = 2 * (1 * w)
= 2 * (55 * 10)
= 1100 ft^2