A train offers economy seat, premium seat and first-class seat. The first-class seats are priced at $20. the remiumn seats are priced at 842 and the economy seats are priced at $8. 1/5 of the seats are economy seats. 2/3 of the remaining seats are premium seats are the rest are first-class seats. On a particular day, the entire train was fully booked and a total of $7,000 was collected from the sale of the train tickets. How many economy seats were there?