The cost of delivery of 10,000 bushels is:

$10,000 \times 400 \text{ cents} = \text{USD } 40,000$

Therefore, Trader X sold: i. 5,000 bushels of wheat to Trader Z for 420 cents per bushel for delivery in June ii. 5,000 bushels to Trader Q for 440 cents per bushel of wheat for delivery in June.

Thus, gross earnings will be:

$5000 \times 420 \text{ cents} + 5000 \times 440 \text{ cents} = \text{USD } 43,000$

Hence, Trader X makes a net profit of:

$\text{USD } 43,000 - \text{USD } 40,000 = \text{USD } 3,000$

This is a classic hedging/speculation scenario where Trader X locks in a purchase price of 400 cents per bushel and then sells portions at higher prices (420 and 440 cents), resulting in a guaranteed profit of USD 3,000 regardless of the spot price in June.