$4.$ Assume the company uses absorption costing and a LIFO inventory flow assumption $($LIFO means last$-$in first$-$out. In other words, it assumes that the newest units in inventory are sold first$)$:

a$.$Compute the unit product cost for Year $1,$ Year $2,$ and Year $3.$

b$.$Prepare an income statement for Year $1,$ Year $2,$ and Year $3.$