Hi, how I can solve this problems? :'c

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2. The owner of a home that is rebuilding her bathrooms tries to decide between toilets that use little water to drain (12 liters per flush) and; ultra water saving toilets (6 liters per flush). Suppose the toilets will be dropped on average 10 times a day and will be replaced in 10 years. The economic model that uses little water will cost S / 400 and the ultra economic model will cost S / 640. If the cost of water is S / 1.50 per 4000 liters, determine which toilet to buy based on a present value analysis using a rate of 12% annual interest.

3. Mr. Perea has his savings in a bank that recognizes 25% annual cash; He wishes to withdraw his deposits and start a business under the following conditions: initial payment of S / 30,000 and 36 monthly installments due of S / 2,500. Mr. Perea expects this business to produce S / 3,500 per month and to sell it at the end of the 5th year at S / 90,000. Will this be a good deal?