$18-23$ : Write the solution of the logistic differential equation

$\frac{dP}{dt}=kP(1-\frac{P}{L})$

in each case. Make a rough sketch of the solution. Find the time needed for the population to reach $95\%$ of its carrying capacity.

$18.k=0\mathrm{.}8,L=4000,$ and $P(0)=500.$

$19.k=0\mathrm{.}08,L=4000,$ and $P(0)=500.$