Astronomer a Claims That the Hubble Constant Is 84 Km/s

Multiple Choice

Astronomer A claims that the Hubble constant is 84 km/s per Mpc, while astronomer B claims that it is 63 km/s per Mpc. If, using the Hubble constant, astronomer A claims that a particular galaxy is 4 billion ly away, then astronomer B would claim that it is _____ billion ly away.

A) 3
B) 5.3
C) 6
D) 2