A builder who specialises in carpentry is thinking about the time that he could spend: Working as a carpenter for which he is paid $30/hr; Working as a painter for which he is paid $20/hr; Playing computer games which he values at $10/hr; Gardening at his own home which he values at $5/hr. All of these activities are mutually exclusive so he can only do one activity at a time. What is his opportunity cost of working as a carpenter?

Select one:

a. $65/hr.

b. $50/hr.

c. $30/hr.

d. $20/hr.

e. $10/hr.