$10.$ Robin$$s Gameroom, a high$-$traffic video arcade, wishes to determine the return on two video machines, Conqueror and Demolition. Conqueror was purchased $1$ year ago for $$30,000$ and currently has a market value of $$31,500.$ During the year, it generated $$900$ of after$-$tax cash receipts. Demolition was purchased $4$ years ago; its value declined from $$13,000$ to $$12,800$ in the year just completed. During the year, it generated $$1,800$ of after$-$tax cash receipts. $(10$ marks$)$