New streetlights will be installed along a section of the highway. The posts for the streetlights will be 7.5 m tall and made of aluminum. The city can choose to buy the posts shaped like cylinders or the posts shaped like rectangular prisms. The cylindrical posts have a hollow core, with aluminum 2.5 cm thick, and an outer diameter of 53.4 cm. The rectangular-prism posts have a hollow core, with aluminum 2.5 cm thick, and a square base that measures 40 cm on each side.
The density of aluminum is 2.7 g/cm3, and the cost of aluminum is $0.38 per kilogram.

a) What is the cost of the cylindrical posts, to the nearest cent?
b) What is the cost of the rectangular-prism posts, to the nearest cent?