If the income elasticity of demand for electricity is + .04 when income is $30,000 per year and quantity demanded is 15,000 kilowatt hours of electricity per year, what is the value of c in the demand function Q = A + bP + cM, where A is a constant, P is price per kilowatt hour and M is average household annual income? (Multiple choice)

1. 20
2. .04
3. -.04
4. -20
5. None of the above.