At 13 50, Ken left Town C for Town D, driving at a speed of 84 km/h. At 15 50, Harry also left Town C for Town D driving at a certain speed. Both of them did not change their speed throughout the journey. At 18 50, both of them passed a bistro that was 252 km away from Town D. How many minutes earlier did Harry reach Town D than Ken?

Distance that Ken travelled
= 5 x 84
= 420 km

Distance between Town C and Town D
= 420 + 252
= 672 km

Since Harry passed the bistro at the same time as Ken, it means that Harry travelled 420 km in 3 hours.

Harry's speed during the journey
= 420 ÷ 3
= 140 km/h

Duration that Harry took to reach Town D after passing the bistro
= 252 ÷ 140
= 1.8 h

Duration that Ken took to reach Town D after passing the bistro
= 252 ÷ 84
= 3 h

Difference between the time they took to reach Town D
= 3 - 1.8
= 1.2 h

1 h = 60 min
1.2 h = 1.2 x 60 = 72 min

Harry reached Town D 72 minutes earlier than Ken.

Answer(s): 72 min