Here's the problem:
It is almost the end of the grading period. I have 730 out of 880 points so far in my math class which means I currently have a B (83%). There are 90 points remaining before grades come out. My teacher rounds each student's score to the nearest percent. What is the fewest number of points I need to get and end up with a grade of

C (at least 70%)__________
B (at least 80%)__________
A (at least 90%)__________


Explain.