A general arranges his soldiers in rows a perfect square. He finds that in doing so, 60, soldiers are left out. If the total number of soldiers is 8160, find the numbers of soldiers in each row. please help Please solve this

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%)