There are two triangles.
Area of a triangle = 1/2 x 10 x 9 = 45 square in.
45 x 2 = 90 square inches
One side is 9 x 9 = 81 square inches.
One side ix 10 x 9 = 90 square inches.
One side = 9 x 13.5 = 121.5 square inches.
Total surface area = 90 + 81 + 90 + 121.5 = 382.5 square inches.
