March (1) = 10 hours (first month, second month.. so on)
April (2) = 12 hours (+2)
May (3) = 14 hours (+2)
June (4) = 16 hours (+2)
July (5) = 18 hours (+2)
August (6) = 20 hours (+2)
September (7) = 22 hours (+2)
October (8) = 24 hours (+2)
November (9) = 26 hours (+2)
December (10) = 28 hours (+2)
Amy works 2 extra hours every month.
By December, she would have worked 28 hours.