Let $\bar{a}=\hat{i}+\hat{j}, \bar{b}=2 \hat{i}-\hat{k}, \bar{c}=3 \hat{i}-\hat{j}+\hat{k}$, then vector $\overline{\mathrm{p}}$ satisfying $\overline{\mathrm{p}} \cdot \overline{\mathrm{a}}=0$ and $\overline{\mathrm{p}} \times \overline{\mathrm{b}}=\overline{\mathrm{c}} \times \overline{\mathrm{b}}$ is

A random variable X has following p.d.f. $\mathrm{f}(x)=\mathrm{kx}(1-x), 0 \leqslant x \leqslant 1 \quad$ and $\quad \mathrm{P}(x>\mathrm{a})=\frac{20}{27}$, then $\mathrm{a}=$

The probability distribution of a random variable X is given by

Then the variance of X is

If $\left(\cos ^{-1} x\right)^2-\left(\sin ^{-1} x\right)^2>0$, then