How can i get item #4?

Problem: 5 coordinates are given: A(-1,4,5), B(2,-1,-2), C(-6, -8, 3) in RCS; D(5, 7, -12) in CCS; and E(8, T/3, 31/2) in SCS. Let point o be the origin. Do the following: 1. Convert the following coordinates given below: a. Coordinate C to CCS: C → C(pC, oC, zC) b. Coordinate C to SCS: CC(rc, OC, C) C. Coordinate D to RCS: DD(xD, YD, 2D) d. Coordinate D to SCS: D D(D, OD, OD) e. Coordinate E to RCS: E EXE, VE, ZE) f. Coordinate E to CCS: E E(PE, DE, ZE) 2. Find the following vectors between two points and find the distance between the two points: a. Vector directed from C to D. Label it as: RCD = RxCD + RyCD + RzCD in RCS b. Vector directed from D to E. Label it as: RDE = RpDE + RODE + RzDE in CCS C. Vector directed from E to C. Label it as: REC = RrEC + ROEC + ROEC in SCS 3. Find the following unit vectors: a. aCD in RCS b. aDE in CCS c. a EC in SCS 4. Find the following: a. From the previous number, convert vector REC SCS to CCS b. The angle between segments AC and AB C. The vector projection of the vector directed from A to B, to vector directed from O to C d. The area of the triangle defined by points A, B, and O e. The unit vector perpendicular to the plane in which the triangle in (d.) is located f. The volume of a parallelepiped if coordinates A, B, C, and O are its corners. g. If vector REC is going to be transferred from point E to A, determine REC as a function of its new components in SCS. h. If the tail of vector REC is at A as in (g.), determine the coordinate of its head in RCS