Senior grades?

How important are first semester senior grades?
To give some background, I got 4A’s & 2B’s and 6A’s (freshman year 1st and 2nd semester), 4B’s & 2A’s and 2C’s & 3A’s & 1B (sophomore), and 4B’s & 2A’s and 6A’s (junior). I haven’t had the best grades but I know it’s most important to keep the upward trend so the only way to keep that would be to get straight A’s senior year first semester, but my econ teacher isn’t rounding up so it looks like I’ll be getting a B in that class. Other than that, I should get A’s in all my other classes. How much will that B hurt me? (I’ve been in almost all honors and AP classes and I have all AP classes this year). It might seem like I’m a bit paranoid but… well yes, I am being paranoid. Please help!

Rule of thumb, No D’s or F’s and maintain your cumulative GPA. You should be fine.

maintain