I didn't grasp this topic too well. can someone help me?

2 hours

Step-by-step explanation:

I'm pretty sure its 2 hrs. If she did not take any breaks, she would have made it in 2 hrs due to her taking a 2 hr break. If its not 2 hours,  its 3. But I am 99% sure its 2 hrs.    

the revenue of the fitness center, y, is the product of two factors: the number of members and the fee paid by each member. there are 320 members now, but number of members goes down by 10 for each $5 increase in fees, so if x is the number of $5 price increases then members is equal to (320 - 10x). since the fee is currently $45, and the fee increases by $5 for every price bump x, the fee is given by (45 + 5x). so, revenue y is given by y = (320 - 10x)(45 + 5x).