不太理解C为何错误？

问题如下：

The following statements are about the methods of pricing deposits. Which of the following statement is NOT correct?

选项：

A.

Pricing deposit-related services at cost plus profit margin: this method matches prices and costs more closely and eliminate many formerly free services.

B.

Conditional Pricing: in this method customer pays a price conditional on his uses of deposit account.

C.

For the marginal cost to set interest rates on deposit: marginal cost = change in total cost = new interest rate × New funds raised at new rate - Old interest rate × Total funds raised at old rate

D.

Relationship Pricing: in this method, pricing deposits according to the number of services the customer uses.

解释：

考点：对Managing and Pricing Deposit Services的理解

答案：C

解析：

C选择错误。再求Marginal cost时，正确的公式应为：

Marginal cost = change in total cost = new interest rate × Total funds raised at new rate - Old interest rate × Total funds raised at old rate