(4) Use vector algebra to answer the following questions. 2 P = -6 = R = -4-4-0 (a) Compute the vectors QP, QR, PQ, PR, RQ, RP. (b) Compute the dot product between each of pairs (QP, QR), (PQ, PR), and (RQ, RP). (c) Decide whether the angles PQR, QRP, and RPQ are acute, right, or obtuse, respectively. (d) Decide whether the triangle with vertices P, Q, R is acute, right, or obtuse; give an answer and justify it. [6+3+6+2=17 marks]