This is applying the formula

We have a slight problem, though, because we are measuring rate in miles per hour, and we are measuring time in minutes. To make this problem solvable, we need to convert to either miles per minute or convert the time to hours. I'm going to convert the 15 minutes into hours:

Now that all of the units match, we have:

You can finish from there I'm sure.
Answer:
I think and sorry if I am wrong but it is 780 ounces
-(x-20)
Basically it’s the same as your other question but your not adding twenty!