A personal-computer salesperson receives a base salary of $\$ 1,000$ per month and a commission of $5 \%$ of all sales over $\$ 10,000$ during the month. If the monthly sales are $\$ 20,000$ or more, then the salesperson is given an additional $\$ 500$ bonus. Let $E(s)$ represent the person's earnings per month as a function of the monthly sales $s$.
(A) Graph $E(s)$ for $0 \leq s \leq 30,000$.
(B) Find $\lim _{s \rightarrow 10,000} E(s)$ and $E(10,000)$.
(C) Find $\lim _{s \rightarrow 20,000} E(s)$ and $E(20,000)$.
(D) Is $E$ continuous at $s=10,000$ ? At $s=20,000 ?$