A movie theater is filled to capacity with $300$ people. After the movie ends, people start leaving at the rate of $100$ each minute.

(a) Find an equation for $N$, the number of people in the theater, as a function of $t$, the number of minutes after the movie ends. Enter your answer as an equation, such as $N = 5t-1$.
help (equations)

(b) For what values of $t$ does the equation make sense in practical terms.
Domain: help (inequalities)