Laura wants to buy a smartphone and agreed to an installment payment plan. Thus, she has to pay 20 dollars the first month, 30 dollars the second month, 40 dollars the third month, and a final installment payment of 90 dollars the fourth month.
Once at home, Laura notes that she does not have enough money in her savings account for the installment payments. Thus, her father offers to double the existing amount in her savings account before each installment payment. Laura is happy with this offer and realizes that she will have exactly the same amount of money at the end of the smartphone payment plan as she did when she started. How much money does Laura have in her savings account? To solution