We can divide the figure into 2 figures:
For the rectangle:
The area of a rectangle is given by:

In this case:
Length = 25ft
Widtth = 15 ft
Then, the area of the rectangle is:

Now, we have two semicircles. When we get together both figures it will convert into a whole circle with a diameter of 15ft.
Now, the area of a circle is given by:

Where r represents the radius.
Also, r = Diameter / 2
Then, the radius is:
r = 15ft/2
r= 7.5 ft
Replace r on the area formula:


Finally, we need to add up to both areas to get the area of the given figure.
Therefore:
Area of the figure = 375ft² + (225/4)π ft²
Area of the figure = 551.6 ft²
Hence, the correct answer is option E.