Zell invested $80,000 in two different types of stocks. The first type earned 9% and the second type earned 12%. If the profit on the 12% stocks was $150 more than the profit on the 9% stocks, how much did Zell invest in the 9% stock?

I'm at a bookstore with $\$35$ in my pocket and a $20\%$-off coupon. what is the cost of the most expensive book i can buy with my money and the coupon? (assume that there are books of every possible price in the bookstore. it's a large bookstore! )