equilibrium? in your city, there are currently three firms providing oil changes. for each firm, there is a fixed cost of $90 per day and a marginal cost of $12 per oil change. each firm currently maximizes its profit by providing 10 oil changes per day. a. for each firm, marginal revenue equals $ nothing. (enter your response rounded to the nearest dollar.) b. this is a long-run, monopolistically competitive equilibrium if ▼ marginal cost price marginal revenue equals $ nothing. (enter your response rounded to the nearest penny.)