if Logb(5)=3.56 and logb(8)=4.61 then what is logb(40)

if Logb(5)=3.56 and logb(8)=4.61 then what is logb(40)

There exists a logarithmic identity which says log(xy) = log(x) + log(y).

Since the two logs above have the same base b, we have:
x = 5 and y = 8. So we have:
logb(40) = logb(5) + logb(8)
logb(40) = 3.56 + 4.61
logb(40) = 8.17