Answer:
the height of the cross section is 3 feet
Explanation:
The computation of the height of the cross section is shown below:
Area = 1 ÷ 2 × (a + b) × h
39 = 1 ÷ 2 × (20 + 6) × h
39 = 1 ÷2 × 26 × h
39 = 26 ÷ 2 × h
39 = 13 × h
h = 39 ÷ 13
= 3 feet
hence, the height of the cross section is 3 feet