Max points

so previously i answered,

(a) start by writing the equation of the circle. (recall that the general form of a circle with the center at the origin is x2 + y2 = r2. (10 points) x^2 + y^2 = 30^2

and

(b) now solve this equation for y. remember the roller coaster is above ground, so you are only interested in the positive root. (10 points) y = √(900 - x^2)

now i have to solve this in the image attached,

any ideas?

Afactory makes propeller drive shafts for ships. a quality assurance engineer at the factory needs to estimate the true mean length of the shafts. she randomly selects four drive shafts made at the factory, measures their lengths, and finds their sample mean to be 1000 mm. the lengths are known to follow a normal distribution whose standard deviation is 2 mm. calculate a 95% confidence interval for the true mean length of the shafts. input your answers for the margin of error, lower bound, and upper bound.