on a coordinate plane triangle uvw has coordinates u v w has coordinates U(20 -20), V'(6, 4.50), and w'(-18,-3).

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%)