The area of the poster is B. 535.5 in².
Explanation:
Step 1:
The poster consists of a rectangle and three-quarters of a circle.
The rectangle has a length of a and width of 3a. The circle has a radius of a.
We calculate the areas of the individual shapes and sum them up to calculate the entire area of the poster.
Step 2:
The area of a rectangle is the product of its length and its width.
If a = 10 inches, the length is 10 inches and the width is 30 inches.
The area of the rectangle

The area of the rectangle is 300 in².
Step 3:
The area of a circle
Here we only have three-quarters of a circle, so
The area of the given circle

Here r = a = 10 inches.
So the area of the circle

The area of the circle is 235.6125 in².
Step 4:
The total area of the shape = The area of the rectangle + The area of the circle.
The total area of the shape

So the area of the poster is B. 535.5 in².