The number of years, n, since two independently evolving languages split off from a common ancestral language is approximated by n ≈ -7600 log r, where r is the proportion of words from the ancestral language common to both languages. Find each of the following to the nearest year.

(a) Find n if r = 0.9. 

(b) Find n if r = 0.3.

(c) How many years have elapsed since the split if half of the words of the ancestral language are common to both languages?