answer: 306in^3
method: I would split the cross-section (the trapezium at the front) into two shapes. You first have your rectangle with dimensions of 4 and 7, and your triangle with dimensions of height 4 and base 3 (10 - 7 = 3). 4 × 7 = 28in^2, 4 × 3 = 12, 12 ÷ 2 = 6in^2. The total surface area of the cross-section is therefore 6 + 28 = 34in^2. Now, to find the volume, you just multiply that by 9 which is 306in^3, which is your answer. I hope this helps!