A bin of 5 transistors is known to contain 2 that are defective. The transistors are tested one at a time until both defective transistors h

A bin of 5 transistors is known to contain 2 that are defective. The transistors are tested one at a time until both defective transistors have been identified. Denote N1 the number of tests until the first defective is identified and N2 the number of tests until the second defective is identified. (a) Find the joint probability mass function of N1 and N2.