The 4 subintervals are given: [2, 4], [4, 7], [7, 9], and [9, 10].
Each subinterval has length: 4 - 2 = 2, 7 - 4 = 3, 9 - 7 = 2, and 10 - 9 = 1.
Over each subinterval, we take the value of the function at the right endpoint: 3, 8, 15, and 18.
Then the integral is approximately
so 78.0 is the correct answer.
