When it rains, the three holes in the garage roof leak water at different rates.  The largest hole leaks at a rate of 3 ounces of water  per minute.  The medium-sized hole leaks water at one-half the rate of the largest hole.  And the smallest hole leaks water at a rate of one-third the rate of the medium-sized hole.  When it rains, what is the combined amount of water, in ounces, that leak from all three holes over a 2-hour time period?
Solve this problem.