Cross-training is a technique that allows team members to share and learn skills from each other. It can enhance team performance, increase flexibility, and reduce risks related to staff turnover or unavailability. It can also improve team cohesion and collaboration. In this scenario, the project manager should allow the engineer and designer to cross-train with each other, as this would benefit both the project and the individuals. The engineer would learn a new skill that is required for the tasks, and the designer would reinforce their existing skill by teaching it. This would also save time and money compared to external training options. Escalating the situation to the engineer’s manager, requesting external training for the engineer, or requesting external training for both the engineer and the designer are not the best choices, as they would not leverage the existing resources and expertise within the team. References: PMBOK Guide, 6th edition, page 339; Professional in Business Analysis (PMI-PBA)® Handbook, page 16.