Wilbur's Bean Emporium serves barbeque sandwiches over the lunch hour. The marginal cost of the 50 th barbeque sandwich is $1.50. The average total cost of the 49 th sandwich is $1.75. For Wilbur's Bean Emporium, __________ when output is 50 sandwiches. Group of answer choices average total costs are falling average variable costs are falling average total costs are rising total costs are falling