How do you do numbers 4 and 5?

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The Lanai Motel's costs at two different sales levels are as follows: Required: 1. Identify each cost as fixed, variable, or mixed. 2. What are the total estimated monthly fixed costs? 3. What are the total estimated variable costs per room sold? 4. Develop a single equation to estimate total costs at various levels of activity. 5. Project the total costs if 3,500 rooms are sold