In the x y-plane, a circle of radius 4 with center on the positive x axis is tangent to the y-axis at the origin, and a circle of radius 10 with center on the positive y-axis is tangent to the x-axis at the origin. What is the slope of the line passing through the two points at which these circles intersect?

**Answer Choices**

A. \dfrac{2}{7}

B. \dfrac{3}{7}

C. \dfrac{3}{7}

D. \dfrac{1}{\sqrt{29}}

E. \dfrac{2}{5}