During his first year at school, Guojun buys eight new college textbooks at a cost of $50

Question:

During his first year at school, Guojun buys eight new college textbooks at a cost of $50 each. Used books cost $30 each. When the bookstore announces a 20% price increase in new texts and a 10% increase in used texts for the next year, Guojun's father offers him $80 extra. Is Guojun better off, the same, or worse off after the price change? Why?