a$.$ A bank has total assets of $$500$ million, total liabilities of $$300$ million, and equity of

$$200$ million. Calculate the bank$$s leverage ratio.

b$.$ A bank$$s total interest income for the year is $$150$ million, and its total interest expense is $$80$ million. If its average interest$-$earning assets are $$2$ billion, calculate its net interest margin $($NIM$).$