Variable manufacturing costs are $$60$ per unit, and fixed manufacturing costs are $$108,120.$ Sales are estimated to be $5,300$ units. How much would absorption costing operating income differ between a plan to produce $5,300$ units and a plan to produce $6,360$ units?

a$.$ $$21,624$

b$.$ No difference

c$.$ $$18,020$

d$.$ $$63,600$