(d) When sales increase by 13%, which of the following should also increase by 13% in a merchandizing company? (You may select more than one answer. Single click the box with the question mark to produce a check mark for a correct answer and double click the box with the question mark to empty the box for a wrong answer.) Variable cost Fixed cost Gross margin Contribution margin Net operating income (e) When sales increase by 13%, which of the following should increase by more than 13% in a merchandizing company? (You may select more than one answer. Single click the box with the question mark to produce a check mark for a correct answer and double click the box with the question mark to empty the box for a wrong answer.) Variable cost Fixed cost Gross margin Contribution margin Net operating income