Draw the Hasse diagram for the partial ordering

a. Draw the Hasse diagram for the partial ordering "x divides y" on the set {2, 3, 5, 7, 21, 42, 105, 210}. Name any least elements, minimal elements, greatest elements, and maximal elements. Name a totally ordered subset with four elements.

b. Draw the Hasse diagram for the partial ordering "x divides y" on the set {3, 6, 9, 18, 54, 72, 108, 162}. Name any least elements, minimal elements, greatest elements, and maximal elements. Name any unrelated elements.