$\text { Find the acceleration vector in terms of } u _ { r } \text { and } u _ { \theta } \text {. }$

Multiple Choice

$\text { Find the acceleration vector in terms of } u _ { r } \text { and } u _ { \theta } \text {. }$
- $r = a ( 5 - \cos \theta ) \text { and } \frac { d \theta } { d t } = 9$

A) $\mathbf { a } = 25 \mathrm { a } ( \cos \theta - 9 \mathrm { a } + \mathrm { a } \cos \theta ) \mathbf { u } _ { \mathrm { r } } + ( 50 \mathrm { a } \sin \theta ) \mathbf { u } _ { \theta }$
B) $\mathbf { a } = 81 \mathrm { a } ( \cos \theta - \mathrm { a } + \mathrm { a } \cos \theta ) \mathbf { u } _ { \mathrm { r } } + ( 162 \mathrm { a } \sin \theta ) \mathbf { u } _ { \theta }$
C) $\mathbf { a } = 81 \mathrm { a } ( 2 \cos \theta - 5 ) \mathbf { u } _ { \mathrm { r } } + ( 162 \mathrm { a } \sin \theta ) \mathbf { u } _ { \theta }$
D) $\mathbf { a } = 81 \mathrm { a } ( \cos \theta + 5 \mathrm { a } - \mathrm { a } \cos \theta ) \mathbf { u } _ { \mathrm { r } } - ( 162 \mathrm { a } \sin \theta ) \mathbf { u } _ { \theta }$