Answer:
A - Sales associate
B - Summer Camp Counselor
Explanation:
First, lets look at how much Joseph would averagely earn from each job.
Cashier in bookstore: in 6 weeks he will earn 900
Summer camp counselor: in 4 weeks 700
Sales associate: in 4 weeks he will earn 850
Overall, becoming a Sales associate will allow Joseph to earn his $850 quicker.
B - the Summer Camp Counselor job will not allow Joseph to make $850 because Summer Camp only lasts 4 weeks.