//chapter 2
//may june 2008
printf("\n");
Pt=15
Aet=2.5;
Aer=0.5;
d=15*10^3;
f=5*10^9;
c=3*10^8;
lamda=c/f;
Pr=(Pt*Aet*Aer)/((d)^2*(lamda)^2);
printf("the radiated power is %gW",Pr);