b) On the circle, midpoint $O(0,0)$ and radius $p$, we have $P(-p,0)$ and $Q(p,0)$ given; also given $W(w,0)$. Choose $A(-\lambda,0)$. On the tangent line $AB$, we choose $B(\beta, \frac{p}{\sqrt{\lambda^{2}-p^{2}}} \cdot (\beta+\lambda)\ )$. On the tangent line $AC$, we find $C(\frac{p^{2}}{\beta},-\frac{p}{\sqrt{\lambda^{2}-p^{2}}} \cdot \frac{\beta \lambda + p^{2}}{\beta}\ )$, using the condition $BC$ is a tangent line. The condition, the circumcircle of $\triangle ABC$ goes through $W$, gives us an expression for $\beta$ as a function of $\lambda,p,w$. Then $\lambda$ is the only parameter and the locus of the point $B$ is part of the circle, midpoint $W$ and radius $w$.