Write the Specified Quantity as a Function of the Specified $A = 7 b$

Multiple Choice

Write the specified quantity as a function of the specified variable.
-The base of an isosceles triangle is half as long as the two equal sides. Write the area of the triangle as a function of the length of the base.

A) $A = 7 b$
B) $\mathrm { A } = \frac { 15 } { 16 } \mathrm {~b} ^ { 3 }$
C) $A = \frac { \sqrt { 15 } } { 4 } b ^ { 2 }$
D) $A = \frac { 15 } { 16 } b ^ { 2 }$