What is the answer to 12 + 35 + 24 + 56 + 92 + 16 + 23 x 23 x 45 x 0 ?

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%)