The information below is extracted from the 2020 Sustainability Report of the NAB (National Australia Bank], one of Australia's 'Big 4' banks. EY provides the financial report audit for the NAB.NAB 2020 sustainability report To provide our stakeholders with a higher level of confidence in our reporting, we engage Ernst & Young (EY) to provide limited assurance over key metrics included in the 2020 Annual Review, the 2020 Sustainability Report and the 2020 Sustainability Data Pack, and limited assurance that NAB has identified and reported on its material themes in the 2020 Annual Review in line with the principles of materiality and completeness as defined by the Global Reporting Initiative. Additionally, KPMG provide reasonable assurance over our Australian National Greenhouse and Energy Reporting (NGER) data (Scope 1 and 2 GHG emissions), along with limited assurance over [various reported energy-related data] Required: (a)Analyse why the different levels of assurance have been given to the different areas of NAB's sustainability operations in the conclusions above. (b) Critically analyse why NAB may be getting its sustainability assurance from two different Big 4 accounting firms. 4 (c) Why is there a demand for, and supply of, assurance on emerging external reports (EER) such as NAB's sustainability report