WHEN Finance Minister P. Chidambaram announced his second budget on February 28, the cynics had a good laugh: to balance the fiscal deficit,Chidambaram had announced a disclosure scheme, where black money would be converted into white at a flat tax rate of 30 per cent. Today, barely seven weeks before the scheme closes on December 31, Chidambaram and his revenue department are having the last laugh: the scheme actually seems to be working.