Question

Check my work: Calculus

Answer 1

Your answer is correct.

Answer 2

check the picture below.

since coordinate for the height of each triangle, is pretty much the left-endpoint y-value, then the upper estimate will be

2(8.7) + 2(7.6) + 2(6.8) + 2(6.2) + 2(5.7)

2(8.7+7.6+6.8+6.2+5.7) => 70.

notice in the picture, that the last endpoint of 5.3, is not really a left-endpoint, so the height of the last rectangle is not 5.3, but 5.7.