Payne Company makes two products, M and N, in a joint process. At the split-off point, 40,000 units of M and 50,000 units of N are available each month. Monthly joint production costs are $270,000. Product M can be sold at the split-off point for $4.20 per unit. Product N can either be sold at the split-off point for $3.20 per unit or it can be processed further and sold for $6.30 per unit. If N is processed further, additional processing costs of $2.50 per unit will be incurred. If N is processed further and then sold, rather than being sold at the split-off point, the change in monthly operating income would be a: A. $30,000 increase B. $315,000 increase C. $155,000 increase D. $125,000 decrease