For the past month, Irene kept a record of the prices at which she purchased gas for her car. She bought 48 litres at $1.04 per litre; 35 litres at $0.97 per litre; 35 litres at $0.89 per litre; and 37 litres at $1.05 per litre. What is the average price-per-litre that Irene paid for gas over the past month?