The Rb-87/Sr-87 Method of Dating Rocks Is Often Used by Geologists

The Rb-87/Sr-87 method of dating rocks is often used by geologists: ${ }_{37}^{87} \mathrm{Rb} \rightarrow{ }_{38}^{87} \mathrm{Sr}+{ }_{-1}^{0} \mathrm{\beta}$ t_1/2 = 6.0 * 10¹⁰ yr.Estimate the age of a rock sample in which the present-day mole ratio of Rb-87 to Sr-87 is 36:1.

A) 2.4 * 10⁹ yr
B) 1.7 * 10⁹ yr
C) 3.1 * 10¹¹ yr
D) 4.1 * 10^-11 yr
E) 3.6 * 10¹¹ yr