SINGAPORE (Reuters) - PSO will buy all seven 87-octane gasoline cargoes it sought for November-December arrival from four suppliers at higher premiums versus July-October purchases, traders said on Wednesday. PSO will pay premiums of $89.00-$96.00 a tonne to Middle East naphtha quotes on a cost-and-freight (C&F) basis to Gunvor, Trafigura, Vitol and Litasco. The state-owned importer was seeking three cargoes, each at 35,000 tonnes, for November arrival and four cargoes for December arrival in a tender which closed on Monday. Offers were valid until Saturday, but traders said it was not uncommon for PSO to finalise the deals earlier once the best offers came in. Based on the best offers, Gunvor will supply three of the seven cargoes while Trafigura will provide two cargoes. Vitol and Litasco will supply one cargo each. The current premiums are higher compared to what PSO had paid for six cargoes for July-October arrival at premiums of $64.30-$74.73 a tonne. Gasoline sentiment has firmed following a fire at Shell's massive 500,000 barrel per day (bpd) Singapore plant in late September. The refinery has partially restarted but Shell has continued to buy cargoes in the Singapore cash window and from nearby refiners to plug the supply shortfall.