When applying the equity method to account for an investment, which of the following represents the correct journal entry to record the amortization of the differential on the investor's books?
a) Debit Differential Expense, Credit Investment in Subsidiary
b) Debit Investment in Subsidiary, Credit Differential Expense
c) Debit Amortization Expense, Credit Investment in Subsidiary
d) Debit Investment in Subsidiary, Credit Amortization Expense