QUESTION $2$

The length intercepted on the staff is $1\mathrm{.}7m$ and the angle that the line of sight makes with a horizontal line is $15\mathrm{.}75$ degree. If the instrument constant is $0\mathrm{.}251m$ and the stadia constant is $100,$ find:

$($a$)$ the horizontal distance of the staff from the centre of the instrument.

$($b$)$ the difference of elevation between the centre of the theodolite and the point where the line of sight intercepts the staff, as indicated by the centre cross$-$wire.