Which expression is equivalent to log8 4a (b-4/c4)?

The
the main rules of the use of logarithm are

loga[a] = 1
loga[AxB] =loga[A] +loga[B] for all value positive of A and B
loga[A/B] = loga[A] - loga[B] for all value positive of A and B

in our case, log8 4a (b-4/c4)

so it is equivalent to log8 4a + log8(b-4/c4) 
and since loga[A/B] = loga[A] l - oga[B] , log8(b-4/c4)  =log8(b-4) - log8(c4)
 
the possible expression:

log8 4a (b-4/c4) = log8 4a + log8(b-4) - log8(c4)

The answer is 15×7=105therefore, 105×5=525 miles