Applying computing technology during problem solving and the reflection of the appropriateness of this application are crucial skills for modern life. This is especially true while working on interdisciplinary STEM problems. However, up to now, few ready-to-use materials are available to foster such competencies. This paper starts bridging this gap by presenting a workbook for students in higher secondary education (around age 15). The workbook focuses on a complex STEM problem, primarily rooted in mathematics, computing, and technology education: Estimating the time it takes to evacuate a building. In the workbook, students work through five exercises focused on the problem of trying to make a sports hall safer. For three potential changes to the building, they should evaluate whether it increases the safety of the sports hall and whether the measure can reasonably be evaluated with a given simulation. During their work, students become aware of arguments useful for such an critical evaluation. For example, a change can only be evaluated if its magnitude is greater than variation in the (randomized) fleeing algorithm of the software. After development of the workbook, we used a design-based research approach to improve its quality. To do so, we asked eight educators for feedback and piloted it with 20 students from two mathematics classes of different capabilities. The results show that students had fun while working on the exercises and both the students and their tutors evaluated the workbook to be educationally relevant. Several issues, most importantly regarding the wording of several exercises, were identified and improved. Multiple exercises were further sub-divided to better suit learners of the age targeted. [For the full proceedings, see ED636095.]