Refer to the Illustration and Find the Length of the Unknown

Multiple Choice

Refer to the illustration and find the length of the unknown side. $a = 3$ and $c = 7$ . Find $b$

A) $b = \sqrt { 39 }$
B) $b = \sqrt { 37 }$
C) $b = \sqrt { 42 }$
D) $b = \sqrt { 44 }$
E) $b = \sqrt { 40 }$