In △PQR, two distinct lines are drawn parallel to QR. The first line ST meets PQ at S and PR at T. The second line UV meets PQ at U (between P and S) and PR at V. The following measurements are known: PS=4cm, SQ=8cm, PT=5cm, TR=10cm and PU=3cm. Answer the following:
a. (i) Find the lengths of PQ and PR.
b. (ii) Calculate the length of PV.
c. (iii) Determine the ratio UV:QR.