Final answer:
The best yield on your investment will be obtained by buying a fund at $10 and selling it at $15, as it provides the highest percentage increase in value.
Step-by-step explanation:
The transaction that will give you the best yield on your investment is option a) A fund that you buy at $10 and sell at $15.
The yield on an investment is determined by the percentage increase in value from the purchase price to the selling price. In option a), the fund increases in value by $5 ($15 - $10), which is a 50% increase from the purchase price of $10. Option b) has a $4 ($5 - $1) increase from the purchase price of $1, which is a 400% increase, and option c) does not provide specific information about the increase in value.
Therefore, option a) is the best choice as it provides the highest percentage increase in value, resulting in the best yield on your investment.