A man had to travel 49 km, which he divided into six stretches which were exact multiples of either 4 km or 5 km. The first four stretches were 4 km 5 km, 8 km and 10 km. Multiples of 4 km and 5 km were travelled at the rates of 40 and 60 km/h, respectively, and between two consecutive stretches, he rested for six minutes. What was his average speed (in km/h) for the whole journey?

A

$$31\frac{7}{11}$$

B

$$32\frac{4}{13}$$

C

$$33\frac{3}{8}$$

D

$$34\frac{4}{15}$$