Choose the One Alternative That Best Completes the Statement or Answers

Choose the one alternative that best completes the statement or answers the question.
-Strontium 90 decays at a constant rate of $2.44 \%$ per year. Therefore, the equation for the amount $\mathrm { P }$ of strontium 90 after $t$ years is $\mathrm { P } = \mathrm { P } _ { 0 } \mathrm { e } ^ { - 0.0244 \mathrm { t } }$ . How long will it take for 15 grams of strontium to decay to 5 grams? Round answer to 2 decimal places.

A) $40.50$ years
B) $450.25$ years
C) $45.03$ years.
D) $4.50$ years