C(x)=x^3 +29x+250

a. 1 less than or equal to x less than or equal to 10

b 10 less than or equal to x less than or equal to 20

the minimum value of the average cost over the interval 1 less than or equal to x less than or equal to 10 is___

(round the the nearest tenth as needed.)

the minimum value of the average cost over the interval 10 less than or equal to x less than or equal to 20 is___

(round to the nearest tenth as needed.)