Question No$.1$:

$[2\mathrm{.}5$ Marks $]$

Calculate elevation of point B if the instrument is set at point A which has elevation of $33\mathrm{.}655$ m $,$ horizontal distance $AB=78\mathrm{.}632m,$ Zenith angle $=100{57}^{\text{'}}{59}^{\text{'}\text{'}},$ height of instrument $($hi$)=1\mathrm{.}281m,$ height of target $(hr)=1\mathrm{.}669m.$ Draw a clear and neat sketch for this problem.