Six employees - Mark, Nathan, Oscar, Penny, Quinn, and Rebekah - must attend a training session. Each employee may choose whether to attend the training session on Monday, Tuesday, Wednesday, or Thursday. Exactly twice as many employees attend the training session on Tuesday relative to Monday. The following conditions apply: Mark and Nathan attend the same training session. Oscar attends the training session on Monday. Penny and Quinn attend different training sessions. Quinn and Rebekah attend different training sessions. Based on the above information, which two employees must attend the same training session