Kylie went into a grocery store and bought 3 apples and 4 bananas, costing a total of $6.50. Lily went into the same grocery store and bought 10 apples and 5 bananas, costing a total of $17.50. Write a system of equations that could be used to determine the price of each apple and the price of each banana. Define the variables that you use to write the system.
3a+4b = 6.50
10a+5b = 17.50