Computing fixed portion of electrical cost-high-low method

Question

The activity of ABC Company for the first six of the current year is as given as below:

Month        Machine Hours       Electrical Cost
January                2,000                 $1,560
February              3,000                 $2,200
March                  2,400                 $1,750
April                      1,900                $1,520
May                      1,800                $1,480
June                     2,100                 $1,600

By using the high-low method, fixed portion of electrical cost each month would be:

a) $400

b) $760

c) $280

d) $190