Question: A new highway is to be constructed. Design A calls for a concrete pavement costing $85 per foot with a 20-year life; four paved ditches costing $55 per foot each; and three box culverts every mile, each costing $7,000 and having a 20-year life. Annual maintenance will cost $1,800 per mile; the culverts must be cleaned every five years at a cost of $500 each per mile. Design B calls for a bituminous pavement costing $45per foot with a 10-year life;two sodded ditches costing $1.60 per foot each; and four pipe culverts every mile, each costing$2,150 and having a10-year life. The replacement culverts will cost $2,450 each. Annual maintenance will cost $2,700 per mile; the culverts must be cleaned yearly at a cost of $230 each per mile; and the annual ditch maintenance will cost $1.60 per foot per ditch. Compare the two designs on the basis of equivalent worth per mile for a 20-year period. Find the most economical design on the basis of AW and PW if the MARR is 6% per year.