If 10 different balls are to be placed in 4 distinct boxes at random, then the probability that two of these boxes contain exactly 2 and 3 balls is :

A random variable X has the following probability distribution :

X:	1	2	3	4	5
P(X):	K2	2K	K	2K	5K2

Then P(X > 2) is equal to :

In a box, there are 20 cards, out of which 10 are lebelled as A and the remaining 10 are labelled as B. Cards are drawn at random, one after the other and with replacement, till a second A-card is obtained. The probability that the second A-card appears before the third B-card is :

Let A and B be two events such that the probability that exactly one of them occurs is $${2 \over 5}$$ and the probability that A or B occurs is $${1 \over 2}$$ , then the probability of both of them occur together is :