1. (a) Find the units of Z[√-6]. (b) Show that each of the elements 2, 5, 2-√-6 and 2 + √-6 is irreducible in Z[√-6]. (e) Show that neither of 2 or 5 is an associate of 2-√-6 or 2 + √-6 in Z[√-6]. (d) Is Z[√-6] a unique factorization domain? Justify your answer.