You invested $10,000 in two accounts paying 8% and 9% annual interest, respectively. If the total interest earned for the year was $880, how much was invested at each rate?
a) $4,000 at 8% and $6,000 at 9%
b) $5,000 at 8% and $5,000 at 9%
c) $6,000 at 8% and $4,000 at 9%
d) $2,000 at 8% and $8,000 at 9%
