////Given
E=40                                   //W
lembda=6000*10**-10                     //m
h=6.63*10**-34                          //Js
c=3*10**8                            //m/s

//Calculation
n=(E*lembda)/(h*c)

//Result
printf("\n Number    of photons emitted per second are given by  %0.2f *10**19",n*10**-19)
printf("\nThe answers vary due to round off error")