A ray of light travels from an optically denser medium towards rarer medium. The critical angle for the two media is $\mathrm{C}=42°$ the maximum possible angle of deviation of the ray is

We know when a light ray is travelling from denser to rarer medium for I just greater than critical angle we get maximum deviation
i.e, maximum d $=\mathrm{\pi }-2\mathrm{C}$ as shown in the figure here we have $\mathrm{C}=42°$
$$\begin{gathered} \therefore \mathrm{d}={\mathrm{\pi }}^{\mathrm{c}}-2\left(42°\right)=180°-84 \\ \mathrm{d}=96° \end{gathered}$$