Mojo Industries tracks the number of units purchased and sold throughout each accounting period but applies its inventory costing method at the end of each period, as if it uses a periodic inventory system. Assume its accounting records provided the following information at the end of the accounting period, January $31.$ The inventory$$s selling price is $$8$ per unit. Required:

Compute the amount of goods available for sale, ending inventory, and cost of goods sold at January $31$ under each of the following inventory costing methods:

a$.$ Weighted average cost.

b$.$ First$-$in$,$ first$-$out.

c$.$ Last$-$in$,$ first$-$out.

d$.$ Specific identification, assuming that the January $10$ sale was from the beginning inventory and the January $17$ sale was from the January $12$ purchase.

$2-$a$.$ Of the four methods, which will result in the highest gross profit?

$2-$b$.$ Of the four methods, which will result in the lowest income taxes?