Ayuda por favor, no quiero reprovar

If sec theta = 5/3 and the terminal point determined by theta is in quadrant 4, then

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%)

Ineed on this question me get the answer