I'm not sure if I am doing this correctly please help. Please show the formulas and any calculations that you do I'm really confused. Thank you so much I really appreciate it!

To produce honey, beekeepers place hives of bees in the fields of farmers. As bees gather nectar, they pollinate the crops in the fields, which increases the yields of these fields at no additional cost to the farmer. What type of externality is present in this case? What might be a reasonable private solution to this externality, and how might the solution be reached