An emergency backup memory system inside a deep-space scientific probe uses a fully charged 5.0 μF5.0\,\mu\text{F}5.0μF capacitor to preserve critical flight data. In the event of a primary power bus failure, the capacitor discharges through a backup circuit path with an effective resistance of 12 MΩ12\,\text{M}\Omega12MΩ.
What fraction of the initial energy stored in the capacitor remains after 1.5 minutes1.5\,\text{minutes}1.5minutes?
1e1.5\frac{1}{e^{1.5}}e1.51
1e3\frac{1}{e^3}e31
1e6\frac{1}{e^6}e61
18\frac{1}{8}81