What a lame cross exam. Algebra uses symbols instead of numbers, right? No, it uses both, symbols and numbers. Okay, and you will agree that if the value of the variables is changed, the answer changes? Mantei is trying to be clever, elicit that the witness recognizes his voice from phone over lunch. Then he tries to set the standard for accepting an opinion, as lack of certainty. Pretty short cross exam, compared with direct.
I anticipate that the redirect by West will be brief.