Carla Vista Limited provides cleaning services to large corporations. Most contracts are two-year contracts under which the company cleans the offices on a monthly basis. On January 1, Carla Vista signed a two-year contract for $34,200 with $6,600 being paid January 31 and the rest monthly at $1,150 per month (end of month). Historically, Carla Vista finds that it spends more time cleaning in the winter and spring and less time in the summer. (a1) When should revenue be recognized?