Lori's Company has the following items: cash in a checking account, $$9,000$; cash in a savings account, $$6,000$; high $-$ grade government securities due in one month $($purchased last month$),$ $$3,536$; accounts receivable, $$3,000.$ How much should appear as Cash and Cash Equivalents on the balance sheet?

A$.$ $$18,536$

B$.$ $$6,000$

C$.$ $$18,000$

D$.$ $$21,536$