Please help if you know.

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

We just started the introduction into circles and i have no idea how to do this.

According to a study done by de anza students, the height for asian adult males is normally distributed with an average of 66 inches and a standard deviation of 2.5 inches. suppose one asian adult male is randomly chosen. let x = height of the individual. a) give the distribution of x. x ~ b) find the probability that the person is between 64 and 69 inches. write the probability statement. what is the probability?