sorry professor but the r=1.25*10^-5 m is =0.125*10^-4 with default ;)

so we have 0.0125 mm=12.5um

-26+19+3=-4 so we have  0.2/1.6*10^-4


on the screen i have a r (with default) of 0.125 unit arbitrary

if we have 1 arbitrary unit= 100um(micrometres) we have:

so we have 1/0.125=100um/x  implies x=12.5um

the radius is effettive 12.5um

thanks