In determining whether or not there is preponderance of evidence, the court may consider: (a) all the facts and circumstances of the case; (b) the witnesses' manner of testifying, their intelligence, their means and opportunity of knowing the facts to which they are testifying, the nature of the facts to which they testify, the probability or improbability of their testimony; (c) the witnesses' interest or want of interest, and also their personal credibility so far as the same may ultimately appear in the trial; and (d) the number of witnesses, although it does not mean that preponderance is necessarily with the greater number