What is the test for determining the amount of unjust enrichment in a tort action?

In measuring the amount of the defendant's unjust enrichment, the plaintiff may present evidence of the total or gross amount of the benefit, or a reasonable approximation thereof, and then the defendant may present evidence of costs, expenses, and other deductions to show the actual or net benefit the defendant received. The party seeking disgorgement has the burden of producing evidence permitting at least a reasonable approximation of the amount of the wrongful gain, and the [r]esidual risk of uncertainty in calculating net profit is assigned to the wrongdoer. (Uzyel v. Kadisha (2010) 188 Cal.App.4th 866, 894, 116 Cal.Rptr.3d 244.)