What is the surface area of a cone with a diameter of 10 inches, a height of 12 inches and a slant height of 13 inches? *

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%)