What is the test for determining the appropriate amount of time spent by an attorney on a personal injury claim?

"Serrano III requires the trial court to first determine a 'touchstone' or 'lodestar' figure based on a 'careful completion of the time spent and reasonable hourly compensation for each attorney ... involved in the presentation of the case.' (20 Cal.3d at p. 48 [141 Cal.Rptr. 315, 569 P.2d 1303]; Serrano v. Unruh (1982) 32 Cal.3d 621, 625 [186 Cal.Rptr. 754, 652 P.2d 985] ... (Serrano IV ).) That figure may then be increased or reduced by the application of a 'multiplier' after the trial court has considered other factors concerning the lawsuit. ¹²