Iodine 131 Is a Radioactive Isotope of Iodine That Is $\mathrm{x}$

Multiple Choice

Iodine 131 is a radioactive isotope of iodine that is used to treat hyperthyroidism. If a sample of 42 milligrams of iodine- 131 is present initially, the number of milligrams that remain after $\mathrm{x}$ days can be modeled by the function $\mathrm{f}(\mathrm{x}) =42 \mathrm{e}^{-0.079 \mathrm{x}}$ . How many milligrams will remain after 5 days? Round to the nearest tenth of a milligram

A) 38.8 milligrams
B) 62.3 milligrams
C) 37.9 milligrams
D) 28.3 milligrams