Priya is buying raisins and almonds to make trail mix. Almonds cost $5.20 per pound and raisins cost $2.75 per pound. Priya spent $11.70 buying almonds and raisins. The relationship between pounds of almonds a, pounds of raisins r, and the total cost is represented by the equation . How many pounds of raisins did Priya buy if she bought the following amounts of almonds:

0.64 pounds of almonds

Round your answer to the nearest hundredth, and do not include units (pounds of raisins).