Three displacement vectors lie along the same straight path: P is 6 cm long pointing right, Q is 4 cm long pointing left, and R is 3 cm long pointing right. With the scale 1 cm → 2 m, which single arrow best represents the resultant displacement?
a) A 7 cm arrow pointing right (+14 m)
b) A 1 cm arrow pointing left (−2 m)
c) A 5 cm arrow pointing right (+10 m)
d) A 5 cm arrow pointing right (+5 m)