(a) (4 points) Write down the four assumptions required to make inferences for a pop- ulation given a sample. (b) (4 points) Propose an unbiased estimator for the average annual income in the county. Show that it's unbiased. (c) (4 points) Find the variance of your proposed estimator. Detail how the variance changes as the sample size increases. Is this change a desirable feature

Circle a has a diameter of 7 inches, a circumference of 21.98 inches, and an area of 38.465 square inches. the diameter of circle b is 6 inches, the circumference is 18.84 inches, and the area is 28.26 square inches. part a: using the formula for circumference, solve for the value of pi for each circle. (4 points) part b: use the formula for area and solve for the value of pi for each circle. (4 points)