Final answer:
The question asks for the marginal product of labor when increasing from one to two workers, but without additional data, a specific answer cannot be given. For the second part, the firm's profit-maximizing employment level is where the wage rate equals the marginal revenue product of labor.
Step-by-step explanation:
The question pertains to the concept of marginal product of labor, which measures the additional output generated from employing one more worker.
To find the marginal product of labor as production goes from employing one worker to employing two workers, one would need to subtract the total output with one worker from the total output with two workers.
The provided options are numerical values suggesting that the answer must be one of these. However, the necessary information to calculate the marginal product is missing from the question.
Without specific data regarding the output levels at each employment level, one cannot confidently determine the marginal product of labor between employing one and two workers.
Regarding part b of the question, in a perfectly competitive labor market, the firm's profit-maximizing level of employment would be the point where the wage rate ($12) equals the marginal revenue product of labor.
The marginal revenue product is calculated by multiplying the marginal product of labor by the price of the output. This matching method would help the firm decide how many workers to hire to maximize profits.