Rs. 8000 is invested at 5.5% earning yearly interest of 8000 × 5.5% = Rs. 440
Rs. 5000 is invested at 5.6% earning yearly interest of 5000 × 5.6% = Rs. 280
Rs. 7000 is invested at x% earning yearly interest of 7000 × x% = Rs. 70x
∴ If she had invested her entire initial capital in bank C alone, then her annual interest income = 4% of 20000 = Rs. 800
Hence, option (a).