Answer:
a. Increase $1,000 
Step-by-step explanation:
The computation is shown below:
Decline in value of inventory is 
= $800,000 - $779,000 
= $21,000 
Now 
Gain on Future contract at year end is 
= $800,000 - $780,000 = $20,000 
 So, 
Net gain or (loss) is 
= $20,000 - $21,000 
= ($1,000) 
As it can be seen that the cost of goods sold rise by $1,000 
 Hence option A is correct.