A company produces two joint products, P and Q, and generates a by-product, R, from a common production process. The total joint production costs up to the split-off point are $600,000. Product P has a final sales value of $350,000, product Q has a final sales value of $200,000, and the by-product R has a final sales value of $50,000. Allocate the joint production costs to each product using the net realizable value method, considering the by-product and joint products.