photo electric effect

a light of wavelength λ is incident on a metal sheet of work function 2ev. The wavelength I varies with time as I=3000+40t., where I is in A and t is in sec.The power incident on the metal surface is 100W. the signal is switched on and off at a regular intervals of 2 mins & 1 mins respectively. . each time the signal is switched on wave length starts from 3000A . the efficiency of photoemission is 1%. (hc=12400ev)
1)Time after which the photo emission stops??
2)No. of photo beams emitted from beam in one hour??
3)variation of rate of emission Vs Time????

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