As a supervisor, you have done everything you can to prepare for a meeting, including writing up and distributing an agenda. At the meeting, you have problems with two of the participants. Ken dominates the conversation, drifting off to subjects that are not on the agenda. Sheryl refuses to talk at all, even though you know she has read the agenda and probably has something insightful to contribute. What steps might you take to elicit more positive participation from Ken and Sheryl?