I have a 2.5-acre lawn with an average slope of 8 degrees and 72 trees to cut around. One smaller section of lawn has a 17-degree slope and another has an 11-degree slope. I am not sure what type of mower to get, zero-turn, tractor or commercial grade walk behind. I would like to spend $3-5k on the unit. I am not planning on using the mower for anything other than cutting grass. Please recommend a type of mower and manufacture/model if you can.