A ray of light coming from the point \( P(1, 2) \) gets reflected from the point \( Q \) on the \( x \)-axis and then passes through the point \( R(4, 3) \). If the point \( S(h, k) \) is such that \( PQRS \) is a parallelogram, then \( hk^2 \) is equal to:
