PLEASE HELP!!! Multiply the top trinomial by the last term in the bottom to normal place each results in the blank spaces provided four step for added three partial products to find the final answer place the results at the bottom.

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%)