first, find the area of the shelf if it were a full circle.
the formula for the area of a circle is a=pi(r squared)
a=pi (10.5 squared)
a=pi x 110.25
a=3.14 x 110.25
a=346.185
now, you have to divide that area by 4 to get the area of the 1/4 circle
346.185/4=86.55
