TRADING volumes in Guoco Group shares and warrants changed significantly in the days leading up to the announcement that the group had won government approval to buy Overseas Trust Bank. The graphs show a change in the pattern of prices and dealing in the warrants and shares on July 12. Financial Services Secretary Michael Cartland said recently that the unusual trading had forced his department to hold talks with Guoco and regulators. It was agreed that a statement would be issued that day by Guoco and the Government confirming that there had been talks between them about Guoco taking over the bank. A few days later, on July 20, turnover of the warrants, which had averaged less than 100,000 a day in June, jumped to 4.4 million. The warrant's price leapt more than 20 cents to $6.53. This was three days before the Government announced that Guoco would take over the bank. There were 455,100 warrants traded on July 26, the first trading day after the announcement.