Mark is absolutely fully capable

I'm confused,

Explanation:

coordinates of r(b,c)

slope of nm is 0.

step-by-step explanation:

the midpoint of the line joining the points (x₁,y₁) and (x₂,y₂) is given by

the midpoint of the line segment nk is given by

∴r(b,c)

the slope of the line joining the points (x₁,y₁) and (x₂,y₂) is given by

slope of rs is

hence

coordinates of r(b,c)

and slope of nm is 0.