The watt is the derived SI unit of power, the measure of energy per unit time

The watt is the derived SI unit of power, the measure of energy per unit time: 1 W = 1 J / s. A semiconductor laser in a CD player has an output wavelength of 780 nm and a power level of 0.10 mW.
How many photons strike the CD surface during the playing of a CD 69 minutes in length?