At last week's hockey game involving the Waterloo Blueberries, the price of a platinum ticket was $25, the price of a gold ticket was $10, the price of a silver ticket was $5, and the price of a bronze ticket was $1. Ophelia buys 10 tickets with an average cost of $14. Suppose that she buys n more platinum tickets. The new average cost of the tickets that she has bought is $20. What is the value of n? Explain how you obtained your answer