The third side is 4
So Pythagorean's theorem is the following

From here we can input the following information that we know

Side B would be about 7.56 if you use trig.
Write and solve an equation of ratios:
15 min 3 racks
---------- = -------------
x 36 racks
Solving this for x: 3x = (15)(36) => x = 180 minutes.
convert this into hours: 180 min 1 hr
------------ * -------------- = 3 hrs (answer)
1 60 min