Fill in the blanks. When choosing the levels of two activities, A and B, in order to maximize total benefits within a given budget:
a. If at the given levels of A and B, MB/P of A is__________ MB/P of B, increasing A and decreasing B while holding expenditure constant will increase total benefits.
b. If at the given levels of A and B, MB/P of A is__________ MB/P of B, increasing B and decreasing A while holding expenditure constant will increase total benefits.
c. The optimal levels of A and B are the levels at which __________equals__________.