-Grant Has Four Hours of Time to Divide Between Studying

Multiple Choice

$$\begin{array} { | c | c | c | } \hline { \text { Figure 1-1 } } \\\hline \begin{array} { c } \text { Haurs } \\\text { Studying }\end{array} & \begin{array} { c } \text { Physics } \\\text { Scare }\end{array} & \begin{array} { c } \text { Gedlay } \\\text { Scare }\end{array} \\\hline [ & 4 [ & 3 [ \\\hline 1 & 50 & 60 \\\hline 2 & 60 & 80 \\\hline 3 & 85 & 90 \\\hline 4 & 90 & 100 \\\hline\end{array}$$
-Grant has four hours of time to divide between studying for a physics exam and a geology exam.Figure 1-1 shows his estimates of the grades (on a scale of 0 to 100) that he could earn from studying a particular number of hours on each subject.If he plans on spending three hours studying physics,what would be his opportunity cost of an additional hour studying physics?

A) 10 points on his geology exam
B) 20 points on his geology exam
C) 30 points on his geology exam
D) 25 points on his physics exam
E) 85 points on his physics exam