Hi, I need help. I was told by another tutor that the answer to number 9 is null set but the program says it's wrong. The program said the answer entered for #7 is right but #9 is wrong. Can you help me?

Find the amount in a continuously compounded account for the given condition. principal: $1000, annual interest rate: 4.8%, time: 2 yr

The function a represents the cost of manufacturing product a, in hundreds of dollars, and the function b represents the cost of manufacturing product b, in hundreds of dollars. a(t) = 5t + 2 b(t) = 7t - 2t +4 find the expression that describes the total cost of manufacturing both products, a(t) + b(t). a. 7t^2 - 7t + 2 b. 7t^2 + 3 +6 c. 7t^2 + 7t - 6 d. 7t^2 - 3t + 6

Which number produces a rationale number when multiplied by 1/5