The distance covered by a train in $$(5y-1)$$ hours is $$(125y^{3}-1)$$ km. The speed of the train is:

A

$$(5y^{3}-1)\ \frac{km}{h}$$

B

$$(25y^{2}-5y+1)\ \frac{km}{h}$$

C

$$(5y+1)\ \frac{km}{h}$$

D

$$(25y^{2}+5y+1)\ \frac{km}{h}$$