2000010605

The patient took a single dose of $50\mathrm{mg}$ of the drug. Within $3$ hours $40\mathrm{\%}$ of the dose was excreted from his body. The mass $m$ (mg) of the drug in the body after time $t$ (hours) is given by the formula $m(t)=m_0{a}^t$, where $m_0$ (mg) is the initial mass and $a$ is a constant. Calculate how much medicine the patient had in his body after $12$ hours.