Determine Where the Graph of the Function $f ( x ) = 9 x - \sqrt { 4 - x ^ { 2 } }$

Determine where the graph of the function $f ( x ) = 9 x - \sqrt { 4 - x ^ { 2 } }$ is concave upward and where it is concave downward. Also, find all inflection points of the function. Select the correct answer.

A) $\mathrm { CU }$ on $( - 2,2 )$ ,
IP none

B) $\mathrm { CU }$ on $( - \infty , - 2 )$ and $( 2 , \infty ) , \mathrm { CD }$ on $( - 2,2 )$ ,
IP $( - 2 , - 18 )$ and $( 2,18 )$

C) $\mathrm { CD }$ on $( - 2,2 )$ ,
IP none

D) $\mathrm { CU }$ on $( - 2,2 ) , \mathrm { CD }$ on $( - \infty , - 2 )$ and $( 2 , \infty )$ ,
IP $( - 2 , - 18 )$ and $( 2,18 )$