a)For the first time, Moose Ltd (Moose) is required to have its financial statements audited under the Companies Act 2006. Your firm has accepted the audit engagement and has sent a draft engagement letter to Moose's directors. The directors have queried why they need to sign an engagement letter when the requirements of an audit are already set out by law and in auditing standards (ISA). List points for inclusion in your firm's response to the directors' query.