Final answer:
Lydia's unit rate is 1.5 rooms per hour. Additionally, the marginal product of the third painter, when two painters paint 200 square feet and three painters paint 275 square feet, is 75 square feet per hour.
Step-by-step explanation:
The question asks about Lydia's painting unit rate. The unit rate is the amount of work done per unit of time. Since Lydia can paint a room in 2/3 of an hour, her unit rate is one room per 2/3 of an hour, which is equivalent to 1.5 rooms per hour (since 1 divided by 2/3 equals 1.5).
In a different context, suppose two painters can paint 200 square feet in an hour, and three painters can paint 275 square feet in the same amount of time. The marginal product of the third painter is the additional area they can paint compared to two painters. That is the difference in square feet (275 - 200 = 75 square feet per hour).