The Indiana Highway Department wants to construct a new rural highway. The engineering team is considering two designs: a. Design A calls for a concrete pavement costing $90/ft. with a 20-year life, two paved ditches each costing $3/ft., three box culverts each costing $9,000/mile, annual maintenance costs of $1,800/mile, culvert cleaning costs of $450/mile every five years. Design A has a 20-year life. b. Design B calls for a bituminous pavement costing $45/ft. with a 10-year life, two sodded ditches each costing $1.50/ft., three pipe culverts each costing $2,250/mile with a 10-year life, replacement culverts will cost $2,400 each, annual maintenance costs of $2,700/mile, culvert cleaning cost of $225/mile every year, and annual ditch maintenance costs of $3/ft.
Compare the two designs on the basis of equivalent worth per mile for a 20-year period. The interest rate is 6%.