PMP Practice: Document and communicate change impacts

Sky Volkov is leading an agile project for Bold Forge Labs developing a mobile fitness app. The team works in two-week sprints with a stable velocity. Over the past four sprints, the team completed 48, 52, 50, and 54 story points respectively. The product backlog currently contains 412 story points of prioritized work remaining. The product owner has just requested adding a new feature worth 38 story points, which the team agrees is feasible but will require them to defer some current backlog items. The sponsor wants to know the revised number of sprints needed to complete all work if this change is accepted. What is the most accurate estimate?