Use the graph to answer the question that follows. A graph with price on the vertical axis and quantity on the horizontal axis. A typical swoosh shaped marginal cost curve is shown, along with two U shaped average total cost curves; ATC and ATC1, with ATC above ATC1. An arrow points down from ATC curve to ATC1 curve. Which of the following explains the shift indicated on the graph? Variable costs decreased Variable costs increased Fixed costs decreased Total costs increased Indeterminate