Mercedes-Benz of Novi

I am in the market for a new car that I am ready to pay cash (Check) full price for. I test drove a car and moment I walk back into the dealership two sales people said "You took a very long time, this was the only car we had for a test drive". I was out for about 30 - 40 minutes. The sales person who was supposed to work with me even went to the extent of saying it was common sense (as if I am a stupid person). By the way I am the customer and you never call a customer stupid. No one had told me how long I could drive to test the car or that others were waiting. I had taken the care for a short drive and to show it to my wife for her input. In the end we as buyer have a lot of choices and definitely do not deserve to be treated like DIRT.