Two methods of carrying away surface run-off water from a new subdivision are being evaluated:
Method A: Dig a ditch where the first cost is 200,000 bahts and 55,000 bahts of redigging and shaping are required at 5-year intervals forever.
Method B: Lay concrete pipe where the first cost is 450,000 with a replacement required at 50-year intervals at a net cost of 650,000 forever.
At i=12%, which method is better?