Randolph Is Taking Three Courses This Semester: Economics, Statistics, and Finance

Multiple Choice

Randolph is taking three courses this semester: economics, statistics, and finance. He has decided to spend 20 hours per week studying (in addition to attending all his classes) and his objective is to maximize his average grade, which means maximizing the total of his grades in the three courses. The table shows Randolph's estimate of the relation between time spend studying and his grade for each course.

$\begin{array}{cccc}&&\text{grade in}\\\text { Hour's of stuay } & \text { Economics } & \text { Statistics } & \text { Finance } \\\hline 4 & 63 & 54 & 68 \\5 & 72 & 64 & 76 \\6 & 79 & 72 & 82 \\7 & 85 & 78 & 87 \\8 & 88 & 83 & 90 \\9 & 90 & 87 & 93 \\10 & 92 & 89 & 95\end{array}$
-What is the maximum AVERAGE grade Randolph can earn if he studies 20 hours per week?

A) 80
B) 80.3
C) 82
D) 81.7
E) none of the above