100 points if you answer - if it's correct ill give brainliest (01.04 MC)The elevation of city A is 60 feet above sea level; the elevation of city C is 12 feet above sea level. The elevation of city D is 1 over 2 of the elevation of city C.

Part A: Write an expression to represent the elevation, in feet, of city D. (5 points)

Part B: Solve the expression and explain why the answer is negative or positive. (5 points)

At wind speeds above 1000 centimeters per second (cm/sec), significant sand-moving events begin to occur. wind speeds below 1000 cm/sec deposit sand and wind speeds above 1000 cm/sec move sand to new locations. the cyclic nature of wind and moving sand determines the shape and location of large dunes. at a test site, the prevailing direction of the wind did not change noticeably. however, the velocity did change. fifty-nine wind speed readings gave an average velocity of x = 1075 cm/sec. based on long-term experience, σ can be assumed to be 245 cm/sec. (a) find a 95% confidence interval for the population mean wind speed at this site. (round your answers to the nearest whole number.) lower limit cm/sec upper limit cm/sec