Answer:
578.22
Step-by-step explanation:
Oct 1st $ 21,000 at 10%
Dec 6th $ 5,000 at 9%
Dec 16th $ 4,000 at 11%
Principal x rate x time = interest
being rate and time expressed in the same metric.
21,000 x 0.10 x (31 + 30 + 31)/365 = 529.3150685
5,000 x 0.09 x (31-6)/365 = 30.82191781
4,000 x 0.11 x (31 - 16)/365 = 18.08219178
Total interest accrued: 578.2191781