Explanation:
the sum of the area of the inner rectangle and the area of the 2 outer half-circles (that together are the area of one full circle).
the radius of the circles is 10 ft.
so, the diameter (= the width of the inner rectangle) = 2×10 = 20 ft.
so, the area of the inner rectangle is
30×20 = 600 ft²
the area of the combined full circle is
pi×r² = pi×10² = 100pi = 314.1592654... ft²
together that is
914.1592654... ft²