Final answer:
The question requires the use of marginal analysis to decide on how many apples and oranges to buy, but the information provided does not contain necessary details about costs, benefits, or utility to perform this analysis.
Step-by-step explanation:
The student's question involves determining the optimal quantity of apples and oranges to buy using marginal analysis. However, the provided information is not adequate to apply marginal analysis as there are no details about the marginal benefit or marginal cost of purchasing more apples or oranges.
Typically, marginal analysis would require information about the costs and benefits of each additional unit to decide on the purchase quantities. For example, if the price or utility of the fruits changes over the quantity, these changes would affect the decision. Furthermore, the cross-price elasticity of demand shows that a % change in price of oranges leads to a % change in quantity demanded for apples. Without additional context or data about costs, benefits, or budget constraints, it's not possible to determine the optimal purchase mix.