9. The lifetimes of the 60-watt light bulbs produced by the Lucifine Company are distributed randomly with an average lifetime of 560 hours. The percentage of bulbs with lifetimes of x hours or less is approximately modeled by f(x)=- 100 1+e-0.04(x-560) The production manager wishes to find the time x that equals or exceeds the lifetime of 68% of the bulbs. Solve for this time. Round to the nearest hour. 10. An initial investment of $2000 doubles in value in 8.1 years. Assuming continuous compounding, what was the interest rate? Round to the nearest tenth of a percent.