What is the test for determining whether a prosecutor's race-neutral explanation is credible?

At the third step of the inquiry, the issue is whether the trial court finds the prosecutor's race-neutral explanations to be credible. (People v. Lenix, supra, 44 Cal.4th at p. 613.) "'Credibility can be measured by, among other factors, the prosecutor's demeanor; by how reasonable, or how improbable, the explanations are; and by whether the proffered rationale has some basis in accepted trial strategy.'" (Ibid.) The trial court draws upon its contemporaneous observations of the voir dire. (Ibid.)