Urn 1 contains 6 red balls and 4 black balls. Urn 2 contains 5 red ball and 2 black ball. Urn 3 contains 3 red balls and 3 black balls. If an urn is selected at random and a ball is drawn, find the probability that it be red.

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%)