The decimal parts of two numbers taken at random are found to be six places. Probability that second can be subtracted from first one without borrowing is

a. \((\frac 12)^ 6\)

b. \((\frac 9{20})^ 6\)

c. \((\frac {11}{20})^ 6\)

d. \((\frac 3{20})^ 6\)