A brass band with 12 musicians is performing at a concert. The band has 7 songs to perform, each of which contains an improvised solo that can be performed by any of the musicians. If the band picks the musicians to perform each solo at random, what is the probability that :

a) a musician performs at least two solos?

b) a musician performs 3 or 4 solos and the other musicians perform at most one solo?

c) a musician performs 3 or 4 solos?

d)exactly two of the musicians perform all the solos?