When Kiki was young and used to not know anything about quantum physics (she only knew the classical view that energy is delivered continuously by a light beam), her home was lit with an isotropic light source with an output of P=1.5W. At a distance R=3.5m, she placed a foil made of potassium with work function ϕ=2.2eV. Help Kiki determine how many seconds it'd take for the foil to absorb enough energy to emit an electron. Assume that the foil absorbs all the incident energy, and that an emitted electron absorbs the energy incident on a circular surface of radius r=5⋅10−11m, given by the typical radius of an atom.