I am bidding on a large commercial job with over 7500 linear feet of curbing and side walks. They want a 1 time cost to edge in the spring with a mechanical edger and then we will maintain with a string edging... We normally do residential and I would like to get some input on what you guys would charge for a job of this size? Price per linear foot? Or charge by the hour? not sure how long it would take to edge this..