1978 AHSME Problem 12

In \triangle ADE, \measuredangle ADE=140^\circ, points B and C lie on sides AD and AE, respectively, and points A,~B,~C,~D,~E are distinct.* If lengths AB,~BC,~CD, and DE are all equal, then the measure of \measuredangle EAD is

- The specification that points A,B,C,D,E be distinct was not included in the original statement of the problem.

If B=D, then C=E and \measuredangle EAD=20^\circ.

\textbf{(A) }5^\circ\qquad \textbf{(B) }6^\circ\qquad \textbf{(C) }7.5^\circ\qquad \textbf{(D) }8^\circ\qquad \textbf{(E) }10^\circ

Full credit goes to MAA for authoring these problems. These problems were taken on the AOPS website.