$1.$ Classify the following accounts into one of following categories:

a$.$ Assets; b$.$ Liabilities: c$.$ Equity; d$.$ Revenue;

e$.$ Expense; f$.$ Off balance sheet activities $($OBS$)$

$(1)$ Interest on U$.$S$.$ Treasury securities

$(2)$ Surplus and paid$-$in capital

$(3)$ Loan commitments

$(4)$ Interest on NOW accounts $($expense$)$

$(5)$ NOW accounts $($liabilities$)$

$(6)$ Consumer loans $($assets$)$

$(7)$ Leases $($assets$)$

$(8)$ Commercial letters of credit

$(9)$ Retained earnings

$(10)$ Service fees charged on deposit account $($revenue$)$

$(11)$ Provision for loan losses $($expense$)$

$(12)$ Swaps

$(13)$ Federal funds sold

$(14)$ Interest on municipal bonds $($revenue$)$

$(15)$ Retail CDs $($liabilities$)$