Let $t$ be the time in weeks. At time $t=0$, organic waste is dumped into a pond. The oxygen level in the pond at time $t$ is given by

Assume $f(0)=1$ is the normal level of oxygen.

(a) On a separate piece of paper, graph this function.

(b) What will happen to the oxygen level in the lake as time goes on?
Choose One The oxygen level will continue to decrease in the long-run. The oxygen level will continue to increase in the long-run. The oxygen level will eventually return to its normal level in the long-run. It cannot determine based on the given information.

(c) Approximately how many weeks must pass before the oxygen level returns to $80$% of its normal level?
weeks (Round to at least two decimal places.) help (numbers)