A homeowner in a sunny climate has the opportunity to install a solar water heater in his home for a cost of $2,481. 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 question is missing the discount or interest rate that we must use to calculate the answer.

for example, if the interest rate is 5% per year, then this would be a good investment if the homeowner can save $2,481 x 5% = $124.05 per year.

but if the interest rate is 8%, then the homeowner would need to save at least $2,481 x 8% = $198.48 per year.

answer: a. the kind of population living in your neighbourhood.

the census explorer data tool by the us census bureau allows the user to zoom in on any neighbourhood within the united states and find the kind of people residing in that by race and age.  

the tool needs to needs to be used twice – once in order to find what type of people reside in a neighbourhood, and then to see the age groups of the people in the same neighbourhood.