Correct Answer - c.
Given `r=6cm, r_(1)=4cm, h_(1)=8cm`
Let `h=` final height of water column
The volume of the cylindrical water column after the glass piece is put will be
`pir^(2)h=800pi+pir_(1)^(2)h_(1)`
`r^(2)h=800+r_(1)^(2)h_(1)`
`(6)^(2)h=800+(4)^(2)8`
`h=(800+128)/(36)=(928)/(36)=25.7cm`
There are two shifts due to glass block as well as water Total shift`=(2.66+4.44)=7.1cm` above the bottom.