//chapter 3
//example 3.10
//page 93
printf("\n")
printf("given")
Eo=21;Vf=.7;Il=40*10^-3;t1=7.19*10^-3;t2=1.16*10^-3;
Vp=Eo+(2*Vf)
Vr=Vp
If=Il/2
Ifrm=Il*(t1+t2)/t2
Ifsm=30;
Rs=Vp/Ifsm
printf("surge limiting resistance is %3.3fohm\n",Rs)