a) State general vector for point on line, e.g.

$ - 5i + 3j + 6k + s\left( {10i + 5j - 5k} \right)$ or $5i + 8j + k + t\left( {10i + 5j - 5k} \right)$ or equiv

Substitute their line into equation of plane and solve for parameter

Obtain correct value, $s = \frac{2}{5}$ or $t =  - \frac{3}{5}$ or equivalent

Obtain (–1, 5, 4) o.e.

b) State or imply normal vector to $p$ is $2i - j + 4k$

Carry out process for evaluating scalar product of two relevant vectors

Using correct process for moduli, divide scalar product by the product of the moduli and evaluate arcsin(..) or arccos(..) of the result.

Obtain ${5.1^ \circ }$ or $0.089$ rads