The half life of radioactive isotope 'X' is 50 years. It decays to another element 'Y' which is stable. The two elements 'X' and 'Y' were found to be in the ratio of 1 : 15 in a sample of a given rock. The age of the rock was estimated to be :

Question

( A ) 150 years
( B ) 250 years
( C ) 200 years
( D ) 100 years