If the position vectors of the vertices of $\Delta ABC$ are $2\hat{i} + 4\hat{j} - \hat{k}$,$4\hat{i} + 5\hat{j} + \hat{k}$,and $3\hat{i} + 6\hat{j} - 3\hat{k}$,then which of the following angles is a right angle?

If $3$ vectors $a, b, c$ are such that $a \neq 0$ and $a \times b = 2(a \times c)$,$|a| = 1$,$|c| = 1$,$|b| = 4$,and the angle between $b$ and $c$ is $\cos^{-1}\left(\frac{1}{4}\right)$,and $b - 2c = \lambda a$,then $\lambda = $

$\bar{a}, \bar{b}, \bar{c}$ are three non-coplanar and mutually perpendicular vectors of same magnitude $K$. If $\bar{r}$ is any vector satisfying $\bar{a} \times ((\bar{r}-\bar{b}) \times \bar{a}) + \bar{b} \times ((\bar{r}-\bar{c}) \times \bar{b}) + \bar{c} \times ((\bar{r}-\bar{a}) \times \bar{c}) = \bar{0}$, then $\bar{r} =$

If $|a \times b| = 4$ and $|a \cdot b| = 2$,then $|a|^2 |b|^2 = $

It is given that $a, b, c$ are vectors of lengths $6, 8, 10$ respectively. If $a$ is perpendicular to $(b+c)$, $b$ is perpendicular to $(c+a)$, and $c$ is perpendicular to $(a+b)$, then the length of the vector $a+b+c$ is (in $\sqrt{2}$)

If $\overline{p}=2 \hat{i}+\hat{k}$,$\overline{q}=\hat{i}+\hat{j}+\hat{k}$,$\overline{r}=4 \hat{i}-3 \hat{j}+7 \hat{k}$ and a vector $\overline{m}$ is such that $\overline{m} \times \overline{q}=\overline{r} \times \overline{q}$ and $\overline{m} \cdot \overline{p}=0$,then $\overline{m} = \dots$