Answer:
Total profit
Step-by-step explanation:
A profit maximising firm is one which marginal revenue exceeds marginal cost in its operations.
Price, inputs, and outputs are determined in such a way that they will realise highest profit.
So when a firm hires an additional worker they weigh the cost of getting his services (salary) against how much they can contribute to the total profit of the firm.
If contribution to total profit exceeds additional salary expense then the firm will go ahead and hire additional workers.