Two vehicles start from places P and Q towards Q and P respectively at the same time. After crossing each other, they complete their journey in 7/2 hours and 18/7 hours respectively. If the second vehicle moves at a speed of 70 km/h, then find the speed of the first vehicle.

A

54 km/h

B

48.6 km/h

C

72 km/h

D

60 km/h