Your Porche's Gas Mileage (In Miles Per Gallon) Is Given $M ( x ) = \frac { 15 } { x + 3,735 x ^ { - 1 } }$

Multiple Choice

Your Porche's gas mileage (in miles per gallon) is given as a function M(x) of speed x in miles per hour. $M ( x ) = \frac { 15 } { x + 3,735 x ^ { - 1 } }$
Calculate $M ^ { \prime } ( x )$ .

A) $\frac { 15 \left( 1 - \frac { 3,735 } { x ^ { 2 } } \right) } { \left( x + \frac { 3,735 } { x } \right) ^ { 2 } }$
B) $\frac { 15 } { 1 - \frac { 3,735 } { x ^ { 2 } } }$
C) $- \frac { 15 \left( x ^ { 2 } - 3,735 \right) } { \left( x ^ { 2 } + 3,735 \right) ^ { 2 } }$
D) $\frac { 15 } { \left( x + \frac { 3,735 } { x } \right) ^ { 2 } }$ ?
E) $\frac { 15 x } { x + 3,735 }$