In addition to corporate purchases, the average price of buying a new, just-released car has increased by 30% in the past 5 years. In the same period, the proportion of car purchases to the average household budget has not changed. Therefore, in the past 5 years The average family budget must also have increased by 30%. The above discussion is based on which of the following assumptions? ['Over the past 5 years, the average number of new home-made cars purchased by each household has not changed.', 'Over the past 5 years, the average family has spent on car-related costs has not changed.', 'Over the past 5 years, the average household expenditure on food and housing has not changed.', 'Over the past 5 years, the cost of spending on new freshly manufactured cars nationwide has increased by 30%.']