1970 AMC 12 Problems/Problem 2

Problem

A square and a circle have equal perimeters. The ratio of the area of the circle to the area of the square is

$\mathrm{(A)}\ \frac 2\pi\qquad \mathrm{(B)}\ \frac pi\root2\qquad \mathrm{(C)}\ \frac 45\qquad \mathrm{(D)}\ \frac 56\qquad \mathrm{(E)}\ \frac 78$ (Error compiling LaTeX. Unknown error_msg)