Victoria sells two types of flour: cake flour and pastry flour. The price of cake flour is $2.50 per kilogram and the price of pastry flour is $4.30 per kilogram.

She decided to mix these two types of flour together and sell it as a new type of flour.

Determine the unit price, in dollars per kilogram, of a mix of 4 kilograms of cake flour and 5 kilograms of pastry flour.