Area of the base of the reservoir=10.8m*3.75m

the pipe is cuboidal in shape:
cross-section area of the pipe=0.075m*0.045m

volume of water through the pipe in 1sec=cross-sectional area * rate of water

This is the volume filled in the reservoir by the pipe in 1sec
so volume filled by the pipe in 30 mins=0.06075*30*60(1 min =60sec)
=109.35 cu.m

This is the total volume in the reservoir after 30 mins.

so height of water level=volume/area of base of the reservoir
=3.24 m
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