1. Problem: A contractor purchases equipment for 50,000 birr, with operating costs of 10 birr/hour for fuel and maintenance and 15 birr/hour for the operator. Customers are charged 50 birr/hour for use. Write total cost, revenue, and profit functions in terms of hours used. 2. Total cost function $C(h)$ includes fixed cost plus variable costs per hour: $$C(h) = 50000 + (10 + 15)h = 50000 + 25h$$ 3. Revenue function $R(h)$ is charge per hour times hours: $$R(h) = 50h$$ 4. Profit function $P(h)$ is revenue minus cost: $$P(h) = R(h) - C(h) = 50h - (50000 + 25h) = 25h - 50000$$ Final answer: - Total cost: $C(h) = 50000 + 25h$ - Revenue: $R(h) = 50h$ - Profit: $P(h) = 25h - 50000$