Here is a polygon. The length are AB=12, BC=9, CD=5, and AD=10 The sidelines of polygon ABCD correspond to the sidelines of EFGH and I JKL

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%)