Help me with this is URGENT pls

Hi, can anyone show me how to do this problem? 100 points for this. in advance

Complete the steps to find 4.830 ÷ 5

Astudent must have an average on five test that is greater than it equal to 80% but less than 90% to receive a final grade of b. devon's greades on the first four test were 78% 62% 91% and 80% what range if grades on the fifth test would give him a b in the course? ( assuming the highest grade is 100%)