The prices of robusta parchment coffee rose at this week's auction on higher buying by exporters, auctioneer J. Thomas & Co said in statement on Friday. Arabica plantation PB grade prices remained unchanged while that of B and C grade fell by 75 - 100 rupees per 50 kg as compared with the previous auction, the statement said. Out of the total 206,269 kg offered for sale, only 64,902 kg were sold at this week's auction.