Let angle of incidence , angle of reflection and angle of refraction be i, r and r' respectively
as per the question ,
$90-r +90 -r'=90$
=> $r'= 90-i$ (because $i=r$ in case of reflection according to Snell's law )
$1 \sin i =y \sin r$
or $\sin i =y \sin r'$
or $\sin i =y \sin (90-i)$
=> $\tan i =y$
or $i=\tan ^{-1} y$
$\qquad= \tan ^{-1} 1.62$
Hence c is the correct answer.