C/D Is the Currency Drain Ratio and R/D Is the Desired

C/D is the currency drain ratio and R/D is the desired reserve ratio. The money multiplier equals

A) $\frac { 1 + C / D } { R / D + C / D }$
B) $\frac { 1 + R / D } { R / D + C / D }$
C) $\frac { 1 + R / D } { 1 + C / D }$
D) $\frac { R / D - C / D } { 1 + R / D }$
E) $\frac { R / D + C / D } { 1 + C / D }$