Triangle N Q L has centroid S. Lines are drawn from each point through the centroid to the midpoint of the opposite side to form line segments N R, L P, and Q M. The length of line segment N S is 9 n minus 12 and the length of line segment S R is 3 n.
S is the centroid of triangle NQL.
What is the length of NR?
4 units
8 units
36 units
48 units