The Carolina Products Company has just completed a flexible budget analysis of its operating income, as shown below.

	Actual	Revenue or Spending		Flexible	Volume/ Activity		Planning
	Results	Variance		Budget	Variance		Budget
Units/volume	12,800	0		12,800	800	F	12,000
Sales revenue	$62,720	$1,280	U	$64,000	$4,000	F	$60,000
Variable expenses	27,520	640	U	26,880	1,680	U	25,200
Contribution margin	35,200	1,920	U	37,120	2,320	F	34,800
Fixed expenses	34,100	100	U	34,000	0		34,000
Operating income/(loss)	$1,100	$2,020	U	$3,120	$2,320	F	$800

Based on the above data, which of the following statements would be a correct interpretation of the $4,000 favorable volume/activity variance for sales revenues?

Group of answer choices

Increase in price per unit

Increase in variable costs

Increase in sales volume

Increase in fixed costs