Will my acceptance be revoked?

Hello all!

I’ve been accepted to UC Merced (not a super competitive school) for mechanical engineering. Last semester, I received a 68% in my honors physics 2 class, and UC Merced allowed me to continue with my admission. However, this semester, I have a B in Physics, but a 69% in IB Calculus. What are the chances they’ll drop my admission? Also, I was approved for deferment for a semester so I can volunteer overseas so I would think I’m on quite a thin wire as it is.

Both of these classes are far beyond what I need to graduate high school, and are considered electives.

Thanks!
Reid