What is the standard of review for application of the power site formula?

Where, as here, the district court must answer a mixed question of law and fact, the standard of review is determined by whether the question is predominantly legal or factual. "If the application of the rule of law to the facts requires an inquiry that is 'essentially factual,' ... founded 'on the application of the fact-finding tribunal's experience with the mainsprings of human conduct' ... [then it is] reviewable under the clearly erroneous standard." United States v. McConney, 728 F.2d 1195, 1202 (9th Cir.1984), citing Commissioner v. Duberstein, 363 U.S. 278, 289, 80 S.Ct. 1190, 1198-99, 4 L.Ed.2d 1218 (1960). However, if the district court must "exercise judgment about the values that animate legal principles," then review must be de novo. Id. Here, application of the power site formula is predominantly factual and therefore must be reviewed for clear error.

b. Application of the Formula