Mobile Inc., manufactured 700 units of Product A, a new product, during the year. Product A's variable and fixed manufacturing costs per unit were $5.00 and $2.00, respectively. The inventory of Product A on December 31 of the year consisted of 100 units. There was no inventory of Product A on January 1 of the year. What would be the change in the dollar amount of inventory on December 31 if the direct costing method was

a) $800 decrease.

b) $200 decrease.

c) $500 decrease.

d) $200 increase.