The Manufacturing Cost of Calico Industries for Three Months of the Year

The manufacturing cost of Calico Industries for three months of the year are provided below: ​
Using the high-low method,the variable cost per unit and the total fixed costs are

A) $0.78 per unit and $4,000
B) $0.40 per unit and $8,000
C) $4.00 per unit and $800
D) $7.80 per unit and $4,000