Which of the following is not tetrahedral?

If $\vec{a} = \hat{i} - \hat{j} - \hat{k}$ and $\vec{b} = \lambda \hat{i} - 3\hat{j} + \hat{k}$ and the orthogonal projection of $\vec{b}$ on $\vec{a}$ is $\frac{4}{3}(\hat{i} - \hat{j} - \hat{k})$,then $\lambda$ is equal to

The locus of the centroid of the triangle with vertices at $(a \cos \theta, a \sin \theta)$,$(b \sin \theta, -b \cos \theta)$ and $(1, 0)$ is (where $\theta$ is a parameter).

If $\log x : \log y : \log z = (y - z) : (z - x) : (x - y)$,then

$A$ car is moving at a speed of $40 \, m/s$ on a circular track of radius $400 \, m$. This speed is increasing at the rate of $3 \, m/s^2$. The acceleration of the car is ....... $m/s^2$.

The area (in sq. units) of the region described by $\{(x,y): y^2 \le 2x \text{ and } y \ge 4x - 1\}$ is