Ernie's Earmuffs produces 200 earmuffs per year at a total cost of $2000 and $400 of its cost is fixed. If he increases output to 220 earmuffs, his total cost increases to $2,100, and his fixed cost remains $400.00. What is Ernie's marginal cost per earmuff?

a. $9.55

b. $35.00

c. $5.00

d. $105.00