In 2017, Erin purchased a solar system to generate electricity for her home, at a cost of $5,000.

a. How much is her tax credit in 2017? b. If she had purchased a solar heating system for her swimming pool at a cost of $3,500, how much could she claim as a tax credit? c. If she had purchased a $5,000 solar electric system and a $4,500 solar heating system for her principal home (not for the swimming pool), how much could she claim as a tax credit? d. If she had purchased the electric system for her principal residence and the solar heating system for a second residence, how much could she claim as a tax credit?