Calculate the missing numbers in the following situations. $($Input all amounts as positive values.$)$

$\backslash$table$[[,,$a$,,$b$,,$c$],[$Invoice cost of merchandise purchases,$$,44,900,$$$,21,900,$$$,17,150],[$Purchase discounts,,$2,900,,,,370],[$Purchase returns and allowances,,$1,950,,840,,640],[$Cost of transportation$-$in$,$T$,,,2,200,,2,900],[$Merchandise inventory $($beginning of period$),,5,400,,,,4,400],[$Net cost of merchandise purchases,,$45,600,,20,200,,],[$Merchandise inventory $($end of period$),,2,650,,4,200,,],[$Cost of goods sold,,,$$,21,700,$$$,17,965]]$