Fresno Industries Inc. manufactures and sells high$-$quality camping tents. The company began operations on January $1$ and operated at $100\%$ of capacity $(150,000$ units$)$ during the first month, creating an ending inventory of $20,000$ units. During February, the company produced $130,000$ units during the month but sold $150,000$ units at $$500$ per unit. The February manufacturing costs and selling and administrative expenses were as follows:

a$.$Prepare an income statement according to the absorption costing concept for the month ending February $28.$

b$.$Prepare an income statement according to the variable costing concept for for the month ending February $28.$

c$.$What is the reason for the difference in the amount of operating income reported in $($a$)$ and $($b$)?$