The Gateway Arch in St. Louis was designed by Eero Saarinen and was constructed using the equation

y = 211.49 - 20.96 cosh 0.03291765x 

for the central curve of the arch, where x and y are measured in meters and |x| < 91.20.
(a) Graph the central curve.
(b) What is the height of the arch at its center?
(c) At what points is the height 100 m?
(d) What is the slope of the arch at the points in part (c)?