A person had $18000 invested in two accounts, one paying 8% simple interest and one paying 9% simple interest. How much was invested in each account if the interest after 1 year is $1541?
a) $8000 in 8% account, $10000 in 9% account
b) $9000 in 8% account, $9000 in 9% account
c) $10000 in 8% account, $8000 in 9% account
d) $7000 in 8% account, $11000 in 9% account