A man has a rather old car being worth $2000. <br>He saw a secondhand car being worth $8000. He wants to keep his old car until he can buy the secondhand one.<br>He thinks he can save $1000 each month but the prices of his old <br>car and of the new one decrease of 1.5 percent per month.<br>Furthermore this percent of loss increases of `0.5` percent <br>Our man finds it difficult to make all these calculations.<br>Can you help him?<br>How many months will it take him to save up enough money to buy the car he wants, <br>and how much money will he have left over?