The number of yeast cells in a laboratory culture increases
rapidly initially but levels off eventually. The population is
modeled by the function
$$\mathrm{n}=\mathrm{f}(\mathrm{t})=\frac{\mathrm{a}}{1+\mathrm{b} \mathrm{e}^{-0.71}}$$
where t is measured in hours. At time t $=0$ the population is
20 cells and is increasing at a rate of 12 cells/hour. Find the
values of a and b. According to this model, what happens to
the yeast population in the long run?