A firm's only variable input is the number of workers it hires. The marginal product of the first 50 workers is constant at 60 units of output per week. The marginal product of all workers hired after the 50th worker is constant at 10 units of output per week. If the firm pays $30 per worker per week, what is the additional cost of producing the 30th unit of output? Round to two decimal places and do not include a currency symbol. If your answer is $1.275, enter 1.28