How much dispersion will a pulse accumulate in 20 km if it has a dispersion figure of 17 ps/nm/km?

How much dispersion will a pulse accumulate in 20 km if it has a dispersion figure of 17 ps/nm/km?

A.
34 ps/nm

B.
68 ps/nm

C.
340 ps/nm

D.
680 ps/nm

E.
3400 ps/nm