An urn contains `r` red balls and `b` black balls. Column I, Column II If the probability of getting two red balls in first two draws (without replacement) is 1/2, then value of `r` can be, p. 10 If the probability of getting two red ball in first two draws (without replacement) is 1/2 and `b` is an even number, then`r` can be, q. 3 If the probability of getting exactly two red balls in four draws (with replacement) from the urn is 3/8 and `b=10 ,t h e nr` can be, r. 8 If the probability of getting exactly `n` red ball in `2n` draw (with replacement) is equal to probability of getting exactly `n` black balls in `2n` draws (with replacement), then the ratio `r//b` can be, s. 2