Let $A = \frac { 1 } { 2 } b h .$

Multiple Choice

Let $A = \frac { 1 } { 2 } b h .$ If $\frac { d h } { d t } = - 4 , \frac { d b } { d t } = 6,$ when and $h = 6,$ then $\frac { d A } { d t }$ is

A) 12
B) 10
C) 8
D) 6
E) 4