Part A:
Recall that the area of a trapezoid is given by

Where a and b are the lengths of the parallel sides, and h is the height between them.
From the figure, we see that,
a = 50 in
b = 100 in
h = 25 in
Let us substitute these values into the above formula.

Therefore, the area of one trapezoid is 1875 inches squared.
Part B:
The bench is made up of four trapezoids
Since we know the area of one trapezoid so we multiply it by 4 to get the area of the entire bench.

Therefore, the area of the entire trapezoid is 7500 inches squared.