One-third of a journey is covered at a rate of 40 km/h, one-fourth at the rate of 35 km/h, and the rest at the rate of 45 km/h. The average speed for the whole journey (in km/h) is:

A

$$\frac{5670}{187}$$

B

$$\frac{6750}{187}$$

C

$$\frac{6570}{187}$$

D

$$\frac{7560}{187}$$