Determine the Open Intervals on Which the Graph of the Function

Determine the open intervals on which the graph of the function $y = 3 x - \tan x , \left( - \frac { \pi } { 2 } , \frac { \pi } { 2 } \right) \text { is concave upward or concave downward. }$

A) concave upward: $\left( 0 , \frac { \pi } { 2 } \right) ;$ concave downward: $\left( - \frac { \pi } { 2 } , 0 \right)$
B) concave upward: $\left( - \frac { \pi } { 2 } , - \frac { \pi } { 6 } \right) , \left( \frac { \pi } { 6 } , \frac { \pi } { 2 } \right) ;$ concave downward: $\left( - \frac { \pi } { 6 } , \frac { \pi } { 6 } \right)$
C) concave upward: $\left( - \frac { \pi } { 2 } , 1 \right) ;$ concave downward: $\left( 1 , \frac { \pi } { 2 } \right)$
D) concave upward: $\left( - \frac { \pi } { 6 } , \frac { \pi } { 6 } \right) ;$ concave downward: $\left( - \frac { \pi } { 2 } , - \frac { \pi } { 6 } \right) , \left( \frac { \pi } { 6 } , \frac { \pi } { 2 } \right)$
E) concave upward: $\left( - \frac { \pi } { 2 } , 0 \right) ;$ concave downward: $\left( 0 , \frac { \pi } { 2 } \right)$