For $X \sim B(n, p)$,if $p=0.6$ and $E(X)=6$,then $\operatorname{Var}(X)=$

An urn contains $25$ balls of which $10$ balls bear a mark $'X'$ and the remaining $15$ bear a mark $'Y'$. $A$ ball is drawn at random from the urn,its mark is noted down and it is replaced. If $6$ balls are drawn in this way,find the probability that all will bear $'X'$ mark.

Ten eggs are drawn successively with replacement from a lot containing $10 \%$ defective eggs. Find the probability that there is at least one defective egg.

$A$ person can kill a bird with a probability of $3/4$. He tries $5$ times. What is the probability that he may not kill the bird at all?

India and Pakistan play a $5$-test hockey series. What is the probability that India wins at least three games?

$A$ die is thrown again and again until three sixes are obtained. Find the probability of obtaining the third six in the sixth throw of the die.