A jar contains six red marbles, four green marbles, and five yellow ones.
a) Determine the number of ways in which any three marbles can be selected.
(3 marks)
b) Determine the number of ways to select four marbles where two are red and two are yellow. (3 marks)
c) Determine the number of ways in which six marbles can be selected where two are red, two are green, and two are yellow. (3 marks)