To calculate average variable cost $($AVC$)$ at each output level, divide the variable cost at that level by the total product. Which of the following is true of average variable cost $($AVC$)?$ PA$.$ In the long$-$run, AVC remains constant but if production increases beyond a particular point, inefficiencies in the fixed$-$size production facility cause AVC to rise.B$.$ In the short$-$run, AVC remains constant but if production increases beyond a particular point, AVC tends to fall.C$.$ In the short$-$run, AVC remains constant but if production increases beyond a particular point, inefficiencies in the fixed$-$size production facility cause AVC to rise.D$.$ In the long$-$run, AVC remains constant but if production increases beyond a particular point, AVC tends to fall,