Sir, - Iarnrod Eireann/CIE are being rightly taken to task in your columns lately on account of their bafflingly Kafkaesque approach to maximising passenger inconvenience. I too visited this theatre of the absurd when I attempted to purchase a ticket on the airport bus from Busaras. As he was unable to furnish me with 50p change from £3, the driver issued me a refundable receipt.On my return journey into town three days later, I was astonished to be told that the receipt could not be offset against that day's £2.50 fare but could only be reclaimed in person from Dublin Bus head office in O'Connell Street.Would Dublin Bus care to explain the logic of this one? - Yours, etc.,Ray McCarthy,Fitzwilliam Street Lower,Dublin 2.