A box contains four black pieces of cloth, two striped pieces, and six dotted pieces. A piece is selected randomly and then placed back in the box. A...

 A box contains four black pieces of cloth, two striped pieces, and six dotted pieces. A piece is selected randomly and then placed back in the box. A second piece is selected randomly. What is the probability that:

a. both pieces are dotted?

b. the first piece is black and the second piece is dotted?

c. one piece is black and one piece is striped?