Given triangle PQR, right-angled at Q, and XY parallel to QR. If PQ is 6cm and PY is 4cm, with PX:XQ = 1:2, calculate the length of PR and QR.

a) PR = 6cm, QR = 12cm
b) PR = 8cm, QR = 12cm
c) PR = 10cm, QR = 15cm
d) PR = 12cm, QR = 18cm