What should be the diameter of a soap bubble, in order that the excess pressure inside it is 51.2N/m2 ? (S. T of soap solution = 3.2/100 N/m)

For a soap bubble , excess pressure is given by dP = 4T/r       ( T = S.T and r = radii)

so,  51.2 = 4*(3.2/100) / r
         51.2 = 12.8 / 100r
         r= 0.25/100 meters
 so, diameter d= 2r = 0.5 /100 meters = 0.5 * 10^-2 m