Two candidates $A$ and $B$ have attended an interview conducted by a recruitment board for two jobs, If the probability that candidate $A$ will get the job is 0.8 and the probability that candidate $B$ will get the job is 0.7 , then the probability that atleast one of them will get the job is

X denotes the number of times heads that occur in $n$ tosses of a fair coin. If $P(X=4), P(X=5)$ and $P(X=6)$ ate in arithmetic progression. The largest value of $n$ is

The probability distribution of a random variable $X$ is as follows. Then, the mean of $x$ is

Two students appeared simultaneously for an entrance exam. If the probability that the first student gets qualified in the exam is $\frac{1}{4}$ and the probability that the second student gets qualified in the same exam is $\frac{2}{5}$, then the probability that atleast one of them gets qualified in that exam is