Answer:
546
Explanation:
The lateral area is made up of 4 faces that do not includes the bases.
2 faces have dimensions 2.5 ft by 21 ft.
2 faces have dimensions 10.5 ft by 21 ft.
LA = 2 * 2.5 ft * 21 ft + 2 * 10.5 ft * 21 ft
LA = 105 ft^2 + 441 ft^2
LA = 546 ft^2
Answer: 546