1954 AHSME Problem 30

A and B together can do a job in 2 days; B and C can do it in four days; and A and C in 2\frac{2}{5} days. The number of days required for A to do the job alone is:

\textbf{(A)}\ 1 \qquad \textbf{(B)}\ 3 \qquad \textbf{(C)}\ 6 \qquad \textbf{(D)}\ 12 \qquad \textbf{(E)}\ 2.8

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