The amount of a sample remaining after $t$ days is given by the equation $P(t)=A\left(\frac{1}{2}\right)^{\frac{t}{h}}$, where $A$ is the initial amount of the sample and $h$ is the half-life, in days, of the substance. A scientist has a 10-mg sample of a radioactive isotope. The isotope has a half-life of 8 days. After 16 days, how much of the radioactive isotope remains?

A7.1 mg

B2.0 mg

C5.7 mg