How can tectonic plates move relative to each other ?

I know that I'm late but, the correct answer is:

The Earth's outer crust (the lithosphere) is composed of a series of tectonic plates that move on a hot flowing mantle layer called the asthenosphere. Heat within the asthenosphere creates convection currents that cause tectonic plates to move several centimeters per year relative to each other.

1. (1.2kw)x(15/60hours) = .3kwh --> a

2. (5kw)x(90/60hours)x(8cents/kwh) = $0.60 --> d

3. microwave --> 1200 watts = (1.2kw)x(6/60hours) = .12kwh

coffee-maker --> 900 watts = (.9kw)x(10/60hours) = .15kwh

therefore, it requires more energy for the coffee-maker to do the same amount of work.

so the answer is a.