Hi Doyin,
Given that the flow in is 450 ft3/min and ithe rate of change of the can volume at a constant diameter is
dV/dt=d/dt(πr2h)=πr2dh/dt you can solve this for dh/dt which how fast the water level is rising
dV/dt=450 ft3/min
r=60/2 ft =30ft
dh/dt=450/(3.14*900)=.16 ft/mn or about 2"/min
Jim