According to the diagrams below, which pertain to a perfectly competitive firm producing output q and the industry in which it operates. Which of the following is correct? MC ATC AVC P -MR P D q Q O b. The diagrams portray both long-run and short-run equilibrium. O a. The diagrams portray neither long-run nor short-run equilibrium. O d. The diagrams portray long-run equilibrium, but not short-run equilibrium. O c. The diagrams portray short-run equilibrium, but not long-run equilibrium