The news announced a $0.4 oil price rollback this Friday. Mr. Deane decided to only fill his gas tank with 10 liters of gas today and then another 25 liters on Friday. If the cost per liter of gas is $1.4 today, how much will Mr. Deane spend for his 35 liters of gas? Give me reasons, before answering the question
Mr. Deane will spend $1.4 / liter x 10 liters = $14 for the 10 liters of gas today. The price of the gas per liter on Friday will be $1.4 / liter - $0.4 / liter = $1 / liter. So, he will spend $1 / liter x 25 liters = $25 for the 25 liters of gas on Friday. Thus, Mr. Deane will spend a total of $14 + $25 = $39 for the 35 liters of gas. So the final answer is 39.