Shots were exchanged and two men were bound with duct tape Monday morning in what Nevada County Sheriff Keith Royal described as a home invasion robbery of more than 15 pounds of marijuana. Sheriff’s deputies responded to a residence in the 18000 block of Farrell Ravine Road on the San Juan Ridge at just after 8 a.m. after receiving a 911 call that two people had been tied up and needed help. “They found a number of totes and a large amount of marijuana cola strewn along the driveway,” Royal said. The names of the two victims, aged 43 and …