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}