Town A and Town B were located close to each other, and recently merged into one city. Town A had a population with $8\%$ African Americans. Town B had a population with $12\%$ African Americans. After the merge, the new city has a total of $5000$ residents, with $10.88\%$ African Americans. How many residents did Town A and Town B used to have? Write and solve a system equation to answer the following questions.