Mid-project the lead design programmer accepted a job at a competitor and left, and a milestone is approaching. What should the project manager do?

The correct answer is to consult the risk response plan. The departure of a key team member, especially a lead programmer, is a foreseeable event that should have been identified as a risk during planning. The risk response plan would outline pre-defined strategies for mitigating the impact of such an occurrence, such as cross-training, identifying backup resources, or a communication plan. Updating the resource calendar is a subsequent action, not the immediate first step; it reflects the change but doesn't solve the problem. Issuing a request to the change control board (CCB) is premature; the CCB handles proposed changes to the project baseline, and while a schedule or cost change might result, the immediate action is to address the risk. Assigning tasks to another team member without consulting the risk plan might be a viable solution, but it's an action within a risk response, not the initial step to determine the best course of action.