The half-life of substance X is 45 years and decomposes to substance Y. A sample from substance Z was taken which contained 1.5% of X and 13.5% of Y by mass. If substance Y is not normally found in substance Z, which of the following is the best estimate of the age, in years, of substance Z?

W) 45

X) 100

Y) 140

Z) 270
Y) 140