Solve the Problem $D$ Digits In $t$ Minutes, Where $\mathrm { D } = - 0.4 \mathrm { t } ^ { 2 } + 9 \mathrm { t }$

Multiple Choice

Solve the problem.
-Participants in a memorization experiment were able to recall an average of $D$ digits in $t$ minutes, where $\mathrm { D } = - 0.4 \mathrm { t } ^ { 2 } + 9 \mathrm { t }$ . Use the graph below to estimate the number of digits recalled after 5 minutes.

A) 75 digits
B) 35 digits
C) 15 digits
D) 55 digits