Please solve it.

A box contains 10 colourful marbles. 3 red, 1 purple, 2 yellow and 4 green. a) If you randomly select marbles with replacement, what is the probability that the 3rd green will be selected on the 4th draw? (1.25 mark) b) If you randomly select 6 marbles without replacement, what is the probability that exactly 3 of them will be red? (1.25 mark) c) If you randomly select marbles with replacement, what is the probability that it takes less than 5 draws to get the first purple? (1.25 mark) d) If you randomly select 5 marbles with replacement, what is the probability that less than 3 of them will be red? (1.25 mark)