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