Mondo Snow Removal's cost formula for its vehicle operating cost is $1,980 per month plus $696 per snow-day. For the month of January, the company planned for activity of 13 snow-days, but the actual level of activity was 17 snow-days. The actual vehicle operating cost for the month was $13,430. The activity variance for vehicle operating cost in January would be closest to:

a. $2,402U

b. $2,402F

c. $2,784U

d. $2,784F