The coordinates of the point where the line segment joining A (5, 1, 6) and B(3, 4, 1) crosses the yz-plane are

$\left(0, \frac{17}{2}, -\frac{13}{2}\right)$

Suppose yz-plane divides the line segment joining A and B in the ratio λ : 1. The coordinates of the point C of division are $\left(\frac{3λ+5}{λ+1},\frac{4λ+5}{λ+1}, \frac{λ+6}{λ+1}\right).$

This point lies on yz - plane.

$∴ \frac{3λ+5}{λ+1}= 0 ⇒ λ = - \frac{5}{3}$

Hence, the coordinates of c are $\left(0, \frac{17}{2}, -\frac{13}{2}\right)$.