For the probability distribution of a discrete random variable $X$ as given below, then mean of $X$ is

X = x	-2	-1	0	1	2	3
P(X = x)	$$ \frac{1}{10} $$	$$ K+\frac{2}{10} $$	$$ K+\frac{3}{10} $$	$$ K+\frac{3}{10} $$	$$ K+\frac{4}{10} $$	$$ K+\frac{2}{10} $$

In a random experiment, two dice are thrown and the sum of the numbers appeared on them is recorded. This experiment is repeated 9 times. If the probability that a sum of 6 appears atleast once is $P_1$ and a sum of 8 appears atleast once is $P_2$, then $P_1: P_2=$

If 7 different balls are distributed among 4 different boxes, then the probability that the first box contains 3 balls is

Out of first 5 consecutive natural numbers, if two different numbers $x$ and $y$ are chosen at random, then the probability that $x^4-y^4$ is divisible by 5 is