When observations begin at $t=0,$ a cell culture has 1200 cells and continues to grow according to the function $p(t)=1200 e^{\prime},$ where $p$ is the number of cells and $t$ is measured
in days.
a. Compute $p^{\prime}(t) .$ What units are associated with the derivative and what does it measure?
b. On the interval $[0,4],$ when is the growth rate $p^{\prime}(t)$ the least? When is it the greatest?