Solve the Problem $\mathrm { A }$ Is Able to Memorize Words at a Rate Given By

Solve the problem.
-In a certain memory experiment, subject $\mathrm { A }$ is able to memorize words at a rate given by
$\frac { \mathrm { dm } } { \mathrm { dt } } = - 0.006 \mathrm { t } ^ { 2 } + 0.4 \mathrm { t } \quad$ (words per minute) .
In the same memory experiment, subject $B$ is able to memorize at the rate given by
$\frac { \mathrm { dM } } { \mathrm { dt } } = - 0.012 \mathrm { t } ^ { 2 } + 0.4 \mathrm { t } \quad$ (words per minute) .
How many more words does subject $B$ memorize from $t = 0$ to $t = 19$ (during the first 19 minutes) ?

A) 45
B) 58
C) -14
D) -41