MUMBAI: More than 31 per cent of the chief financial officers (CFOs) from various companies feel implementation of GST is challenging and manufacturing is the most affected sector, according to a recent survey. Further, over 54 per cent CFOs believe that the impact of demonetisation has been neutral, while 56 per cent are “highly optimistic” of the country's macro-economic growth in the next 4-5 years, the Deloitte Annual CFO survey said.“The country remains optimistic about economic prospects, as it remains buoyant post demonetisation and amongst global uncertainties,” the survey report noted. Given the macro-economic trends that point to a possible global growth revival , there will be opportunities to increase exports and investment which have been a concern for the past few quarters, it said.