\([OH]^-\) of final soluton
milliequivalent of \(\mathrm{Ba}(\mathrm{OH})_{2}\)
\(=\frac{-\text { milliequivent of } \mathrm{HCL}}{\text { total volume }}\)
\(=\frac{6-1}{50}=0.1\, \mathrm{M}\)
$A = NH_4Cl$; $ B = CH_3COONa$; $ C = NH_4OH$; $D = CH_3COOH$