Verified Answer :

AL2006

From that information, I can tell that the force pushing on the mass
averaged (282 and 1/3) newtons during those 24 seconds. 

But the information doesn't nail down what the mass must be.
I think it would if we only knew something about the friction.
Either tell us how much friction there is, or tell us that there's
none, and I think I could find the mass.

power = work / time
work = force displacement
force = mass
gravity

so:

power = (mass gravity displacement) / time
726 = (mass 9.81 36 ) / 14
726 14 = mass 9.81 36
10164 = mass
353.16
mass = 10164 / 353.16

mass = 28.78 kg