Even with exact calculation we get nearly the same ans... So we can directly take concentrations as in the first solution.
@Pratime-Jaiswal that is from dissociation of water. Here conc of oh- ion from ca(oh)2 is almost same as conc of oh- from h20 so it cannot be neglected
@VEDANT-ZOPE as per your soln shouldn't ans be B as slipping is happening first?