216.2 ft²
1) The surface area is found by the sum of two times the Base Area and the Side Area.
2) Examining that picture, we can write it out:
2 rectangles: 6.4 x 12
2 rectangles: 1.7 x 6.4
2 rectangles: 1.7 x 12
3) Hence, the total surface area is the sum of those:
S = 153.6 +21.76+40.8
S =216.2 ft² (rounding off to the nearest tenth)