Answer:
Ans.
a) You earn $1,000 for selling 4,000 shares
b) The value of your final inventory is $615,000
Step-by-step explanation:
Hi, what you earn is the spread, which is the difference between the bid and ask quote, that is:

This means that you earn $0.25 per share you sell, therefore your earnings are:

Now, for your final inventory (its value) all you have to do is to multiply your remaining inventory (6,000 shares, because you bought 10,000 and sold 4,000) by the ask quote.

Best of luck.