Use the Chain Rule to Find $\frac { \partial u } { \partial p }$

Multiple Choice

Use the Chain Rule to find $\frac { \partial u } { \partial p }$ .
$$u = \frac { x + y } { y + z }$$
$x = p + 3 r + 4 t , y = p - 3 r + 4 t , z = p + 3 r - 4 t$

A) $\frac { \partial u } { \partial p } = \frac { 12 t } { p ^ { 2 } } + t$
B) $\frac { \partial u } { \partial p } = - \frac { 4 t } { p ^ { 2 } }$
C) $\frac { \partial u } { \partial p } = - \frac { 12 t } { p ^ { 2 } }$
D) $\frac { \partial u } { \partial p } = - \frac { 3 t } { p ^ { 3 } }$
E) $\frac { \partial u } { \partial p } = \frac { 4 t } { p }$