a package contains 12 resistors 3 of which are defective If

a package contains 12 resistors, 3 of which are defective. If 4 are selected, find the probability of getting:

A. 0 defective resistors

B. 1 defective resistor

c. 3 defective resistors

A. 0 defective resistors : 9C4 / 12C4 = 14/55

B. 1 defective resistor : (9C3*3C1)/12C4 = 28/55

c. 3 defective resistors : (9C1*3C3)/12C4 = 1/55