Conditional formatting with multiple criteria in different cells

Hi, I'm new to the forum and I have read many posts and it has been very helpful. I am pretty good at Excel but I have a conditional formatting problem that I cannot seem to figure out. I have activation dates in column L and column K is either listed as Purchase or Lease. I would like to set conditional formatting so the date in column L turns red when 3 years have past (in other words 3 years after the date listed) and then only when column K is listed as Lease. I want it to do nothing if column K is listed as Purchase. If anyone can help I would be very grateful. Thanks!