If the variable selling and administrative expenses totaled $124,000 for the year (80,000 units at administrative expenses totaled $136,500 (78,000 units at $1.75 each), the effect of the quantity factor on the change in contribution margin is: Oa-$3,500 increase Ob. $3,000 increase Oc. $3,000 decrease Od. $3,500 decrease $1.55 each) and the planned variable selling and