A homeowner in a sunny climate has the opportunity to install a solar water heater in his home for a cost of $2900. After installation the solar water heater will produce a small amount of hot water every day, forever, and will require no maintenance. How much must the homeowner save on water heating costs every year if this is to be a sound investment? (The interest rate is 5% per year.

Amanager of a store that sells and installs spas wants to prepare a forecast for january and june of next year. her forecasts are a combination of trend and seasonality. she uses the following equation to estimate the trend component of monthly demand: ft = 30+5t, where t = 1 in january of this year. seasonal relatives are 0.60 for january and 1.50 for june. what demands should she predict for january and june of next year