Find an Equation of the Circle with the Given Center $5.2 \mathrm { ft }$

Find an equation of the circle with the given center and radius.
-A one-way street passes under an overpass, which is in the form of the top half of an ellipse, as shown in the figure. Suppose that a truck 26 feet wide passes directly under the overpass. What is the maximum possible height of this truck to the nearest tenth of a foot?

A) $5.2 \mathrm { ft }$
B) $8.9 \mathrm { ft }$
C) $7.8 \mathrm { ft }$
D) $10.4 \mathrm { ft }$