Ahmed and Ali are both saving money to buy a new computer. Ahmed places $ 300 in a safe and adds $15 to this amount each month. Ali opens a saving account with a $ 400 deposit. He earns 5.5% interest each month on the total amount of money in the account. For each person, the total amount of money saved is a function of the number of months. Find the relationship between the amount of money Ahmed saves and number of months. Determine whether given relationship is linear.