17. Find the number of incongruent solutions of
a) $x^{2} \equiv 31 \quad(\bmod 75)$
b) $x^{2} \equiv 16 \quad(\bmod 105)$
c) $x^{2} \equiv 46 \quad(\bmod 231)$
d) $\quad x^{2} \equiv 1156\left(\bmod 3^{2} 5^{3} 7^{5} 11^{6}\right)$.