The diagram below shows a rectangle with side lengths 4 and 8 and a square with side length 5 . Three vertices of the square lie on three different sides of the rectangle, as shown. What is the area of the region inside both the square and the rectangle?

**Answer Choices**

A. 15 \dfrac{1}{8}

B. 15 \dfrac{3}{8}

C. 15 \dfrac{1}{2}

D. 15 \dfrac{5}{8}

E. 15 \dfrac{7}{8}