4. Natasha has been told that if she reduces the thermostat setting on the heating system at her home by 1 degree, she will be able to reduce her present annual energy consumption of 5,000 kWh by 20%. In doing so, she will be able to save as much as $250 per year. (3.3)

a. What is the implicit cost of 1 kWh of energy consumption?

b. If Natasha reduces the thermostat setting by another degree, she can reduce her annual energy consumption by another 10%. Based on your answer in Part (a), how much more money would she be able to save?