Starr Corp. approved a plan of merger with Silo Corp. One of the determining factors in approving the merger was the strong financial statements of Silo, which were audited by Cox Co., CPAs. Starr had engaged Cox to audit Silo's financial statements. While performing the audit, Cox failed to discover material fraud, which subsequently caused Starr to suffer substantial losses. For Cox to be liable under common law under the Ultramares decision, Starr, at a minimum, must prove that Cox____________.