I'm going to guess that Monday is the worst, because people are miserable they just got into work, as well as swamped with additional work that came about over the weekend. Friday sucks because people want to go home and be done with that week. Few people work on the weekend. Tuesday is best because it must give a person four business days for followup. Any reporter/businessperson/client who wants to reach the company has time to do so over the next few days. That would be my guess.