Given a tetrahedron ABCD with A = (1,1,1), B = (3,2,1), C = (0,1,2) , D = (3,2,2)

a) Find volume of ABCD:

I have

Is that correct?

b) Find distance between A and face BCD:

Face BCD is

But I can't remember the distance formula, any help?

I think is this one:

dist(A,BCD) =

Sorry, we don't have a textbook for this course, and the professor didn't have the formula clearly, I tried my best to take the notes but I just can't follow him.

c) Find the distance between the lines AC and BD:

AC = (1,1,1)+t(-1,0,1) , BD = (3,2,1)+s(0,0,1)

dist(AC,BD) =

Is that right?