I was asked to give an estimate for weed control on 8000 sq ft of flower beds. The customer asked that the weeds be pulled weekly and flowers pruned after they have bloomed. They also wanted me to do a fall cleanup. I am planning on liberally spreading a pre-emergent(snapshot, treflan, or trifluralin) in the spring and early summer so I do not have to pull many weeds. Which pre-emergent is the best? Those of you with experience, what can I expect? What is a ball park figure for this bid? Is it worth the hassle?