Sunrise Foods Limited recently merged with a smaller competitor, Dusk Snacks Nigeria Limited. Post-merger integration revealed that Sunrise Foods had a collaborative, innovation-driven culture, while Dusk Snacks operated a highly hierarchical, compliance-focused culture. According to Edgar Schein's model of organisational culture, which level of culture is MOST difficult to change during post-merger integration?

Edgar Schein's model identifies three levels of culture: artefacts (visible), espoused values (stated beliefs), and basic underlying assumptions (deeply ingrained, unconscious beliefs). Basic underlying assumptions are the most difficult to change because they are taken for granted, rarely questioned, and deeply embedded in employees' worldviews. Artefacts and espoused values are more visible and accessible to change management interventions during integration.