The weight of each bag of coffee beans sold by a shop follows a normal distribution with a mean of 510 g and a standard deviation of 18 g. A bag of coffee beans with weight less than 500 g is considered as below standard, and that with weight less than 485 g is considered as underweight. Dan buys 3 bags of coffee beans from the shop. He will lodge a complaint if at least 2 of them are below standard, and he will return a bag of coffee beans if it is underweight. Given that Dan will lodge a complaint, find the probability that he will return exactly 2 bags of coffee beans?