Find the length of the median AM in the triangle ABC, for the points A(2,1.5,-4), B (3,-4,2) and C(1,3,-7), then find the distance from A to the centroid of the triangle.

Ok, so this is what I did so far, but I am stuck as to where to go to find the distance from A to the centroid of the triangle, plus my answer for the first part does not seem to be correct with the back.

BC Midpoint=(-2,7,-9)

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2

=(-1,7/2,-9/2)

AM=(-3,2,-0.5)

=sqrt (13.5)

that's my answer for part A, above, but the answer in the back says 2.5

For part b, I found the midpoint of each AB, BC, and AC.. but I am not sure how or where to go from here.