b$.$ Assume that more than one product is being sold in each of the following four case situations: $($Enter "Contribution margin ratio" in percent. Round your final answers to the nearest whole dollar amount.$)$

$\backslash$table$[[,$Case #$1,$Case #$2,$Case #$3,$Case #$4],[$Sales$,$$$,540,000,$$$,440,000,,,$$$,640,000],[$Variable expenses,,,,$286,000,,,,448,000],[$Fixed expenses,,,,$110,000,,142,000,,],[$Operating income $($loss$),$$$,9,000,,,$$$,32,000,$$$,(4,600)$