Re: #6
For a student who has a 5 on AP calculus BC, the business major requires taking one of 16B, 1B, 53, or 54, according to https://haas.berkeley.edu/Undergrad/aplist.html . Retaking 16A after a 5 on BC could be seen as grade-grubbing (and some students who retake AP credit slack too much and do not earn the “easy A” that they want). Depending on his backup major(s), it would be better to avoid wasting schedule space on 16A in order to use it to prepare for his backup major(s) as well as business.
He can try the old final exams for 16A, 1A, and 1B to check his knowledge before taking 16B, 1B, 53, or 54. The old exams can be found at https://tbp.berkeley.edu/courses/math/ .
What his backup major(s) are also affects whether he should take 16B or 1B, or needs more advanced math like 53 and/or 54. For the economics major, a 5 on AP calculus BC fulfills its minimum math requirement (otherwise fulfilled by 16B or 1B), but students who want to take the more math option should take 53 and 54.