1950 AHSME Problem 11

If in the formula C =\frac{en}{R+nr}, where e, n, R and r are all positive, n is increased while e, R and r are kept constant, then C:

\begin{array}{l} \textbf{(A)}\ \text{Increases}\qquad\textbf{(B)}\ \text{Decreases}\qquad\textbf{(C)}\ \text{Remains constant}\qquad\textbf{(D)}\ \text{Increases and then decreases}\qquad\\ \textbf{(E)}\ \text{Decreases and then increases} \end{array}

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