Extend line in 3D space

Origin is at [xc,yc,zc] (known)

Point is at [xo,yo,zo] (known)

Original line is from [xc,yc,zc] to [xo,yo,zo]

Need to extend the line and new line will be from [xc,yc,zc] to [xp,yp,zp].

Magnitude distance, d, from [xo,yo,zo] to [xp,yp,zp] is also known. (ie. d=5 units)

How to find [xp,yp,zp] ?

[John D'Errico]

Um, so what have you tried? IF nothing, then why not?

Can you create a vector of unit length that points in the direction of this line? How can you create a vector, given two points in space?

Hint #1: If you divide a vector by the norm of that vector, then the result has unit length, i.e., length will be 1.

Hint:2: If you have a vector that has unit length, and you want it to have length 5, you can multiply it by 5.