If two coins are tossed $5$ times,what is the probability of getting $5$ heads and $5$ tails?

Let a biased coin be tossed $5$ times. If the probability of getting $4$ heads is equal to the probability of getting $5$ heads,then the probability of getting at most two heads is

The probability that a person will develop immunity after vaccination is $0.8$. If $8$ people are given the vaccine,then the probability that all develop immunity is equal to:

If the mean and variance of a binomial variate $X$ are $2$ and $1$ respectively,then the probability that $X$ takes a value greater than $1$ is

$A$ test consists of $6$ multiple choice questions,each having $4$ alternative answers of which only one is correct. The number of ways in which a candidate answers all $6$ questions such that exactly $4$ of the answers are correct is:

Suppose $X$ follows a binomial distribution with parameters $n$ and $p$,where $0 < p < 1$. If $\frac{P(X=r)}{P(X=n-r)}$ is independent of $n$ for every $r$,then $p$ is equal to