Final answer:
To determine Lena's investment in Fund B, we use an equation based on the given percentage returns and total profit. After solving the equation, we find that none of the provided options match the correct investment amount, which is $12000. There appears to be a discrepancy in the question.
Step-by-step explanation:
To find out how much Lena invested in Fund B when both funds together returned a 7% profit, we can set up the following equation:
Let the amount invested in Fund B be x. Since Lena invested $9000 in Fund A at 3% return, her return from Fund A is 0.03 × $9000. The return from Fund B is 0.10 × x because Fund B has a 10% return. Lena's total return at 7% profit on the total investment should equal the sum of returns from Fund A and Fund B.
The total amount invested is $9000 + x. Therefore, our equation becomes:
0.07 × ($9000 + x) = 0.03 × $9000 + 0.10 × x
630 + 0.07x = 270 + 0.10x
Subtract 0.07x from both sides:
630 = 270 + 0.03x
Subtract 270 from both sides:
360 = 0.03x
Divide both sides by 0.03 to isolate x:
x = $12000
However, since this result is not one of the options provided, it seems there might have been a discrepancy in the question. None of the options a, b, c, or d are correct. Lena invested $12000 in Fund B.