Jennifer Crum has an exercise regimen
at the local gym that includes using a treadmill, stair machine,
and cycle. According to a website, a 130-pound person like

Jennifer will burn, on average, about 600 calories per hour run-
ning a moderate pace on the treadmill, about 500 calories per

hour on the stair machine, and about 300 calories per hour on
the cycle. Source: Nutristrategy.
a. Jennifer wants to spend 10 hours a week at the gym, and
would like to spend twice as much time on the stair machine
as the cycle. She wants to burn 5000 calories a week at
the gym. Is this possible? How much time should Jennifer
spend on each machine?
b. Jennifer decides to spend 15 hours this week at the gym.
She still wants to spend twice as much time on the stair
machine as the cycle, but wants to double the total number
of calories that she burns. Is this possible?
c. Next week Jennifer can spend only 9 hours at the gym, and
still wants to spend twice as much time on the stair machine
as the cycle. Can she still burn 5000 total calories? If so,
how much time should Jennifer spend on each machine?