Answer
$\$20,000$ at $3.25\%$ and $\$14,560$ at $1.75\%$.
Work Step by Step
Step 1. After paying tax, she got $48,000\times(1-0.28)=34,560$
Step 2. Assume $x$ amount at $3.25\%$, thus the amount at $1.75\%$ would be $34,560-x$
Step 3. The total annual interest can be found as $0.0325x+0.0175(34,560-x)=904.80$
Step 4. Solve the equation: $0.0325x-0.0175x+604.80=904.80$ or $0.015x=300$, thus $x=20,000$
Step 5. Conclusion: investments $\$20,000$ at $3.25\%$ and $\$14,560$ at $1.75\%$.
