Find the Average Value of the Function $f ( x ) = \frac { x } { \sqrt { x ^ { 2 } + 9 } }$

Multiple Choice

Find the average value of the function $f ( x ) = \frac { x } { \sqrt { x ^ { 2 } + 9 } }$ $0 \leq x \leq 4$ .

A) 0
B) $\frac { 2 } { 5 }$
C) 10
D) $\frac { 1 } { 5 }$
E) $\frac { 1 } { 2 }$
F) 5
G) 4

H) $\frac { 4 } { 5 }$