At the high level of activity in November, 7, 000 machine hours were run and power costs were $18, 000. In April, a month of low activity, 2, 000 machine hours were run and power costs amounted to $9, 000. Using the high-low method, the estimated fixed cost element of power costs is $5, 400. $18, 000. $9, 000. $12, 600