57. The figure shows the graph of \( y=x^{2}-6 x+10 \), where \( x \geq 0 \). \( R(p, q) \) is a point on the graph. \( P(p, 0) \) and \( Q(0, q) \) are points on the \( x \)-axis and the \( y \)-axis respectively.
(a) Express \( q \) in terms of \( p \).
(b) If the perimeter of rectangle \( O P R Q \) is 12 units, find the possible values of \( p \).
1 or 4