12. [4] Are the following partitions of the set {c,o,m,p,u,t,e,r}? If no, why not? a. {{t,e,r},{c,o,m},{u,p}} b. {{t,c,r}, {u,o,e}, {p,m,c}} {{r,e},{t,u},{p,m},{o,c}} c. d. {{c, e, m, o, p, r, t}}