Would anyone know how to compute the answer to the following quesiton(s). The answer to these questions are given in the textbook but i am having difficulty figuring out how they were obtained.

A geneticist has bred three different strains of fruitfly. In her lab, the geneticist currently has 8 strain flies, 6 strain B flies, and 4 strain C flies. Within each strain, the flies are genetically and phenotypically identical.

a) if the geneticist randomly seletcs 4 flies, what is the probability that none of them are strain B?

b) if the geneticist randomly selects 4 flies, what is the probability that at least 3 of them are strain A?

c) the geneticist wishes to randomly select 2 flies from each strain for an experiment. In how many ways can this be accomplished?

d) For another experiment, the geneticist will randomly select flies for 3 experiements. The first experiment requires 4 flies, the second and third experiments each require 3 other flies. If the assignment of flies to the 3 experiments is done randomly, what is the probability that each experiment gets exactly 2 strain A flies?

0.162

0.206

2520

0.03455

thanks!