In April $2024,$ Billy$$s start$-$up software firm had a total income of $$10,000$ and a total expense of $$11,000.$ Because the beginning balance from the end of March $2024$ was only $$500,$ Billy used a credit card advance of $$1000$ in April to cover shortfalls. What is the net cash flow of Billy$$s firm in April $2024?$

A$.$

$-$$$1,000$

B$.$

$-$$$500$

C$.$

$$500$

D$.$

$$1,000$