Suppose a cellminusphone manufacturer currently sells 20,000 cellminusphones per week and makes a profit of $5,000 per week. a manager at the plant observes, 'although the last 3,000 cell phones we produced and sold increased our revenue by $6,000 and our costs by $6,700, we are still making an overall profit of $5,000 per week so i think we're on the right track. we are producing the optimal number of cell phones.' refer to the scenario above. had the firm not produced and sold the last 3,000 cell phones, would its profit be higher or lower, and by how much