Factory orders remained weak in April, but firms were their most optimistic in two years about raising output in the coming months, the CBI's monthly Industrial Trends survey showed yesterday. The CBI survey’s total order book balance improved only slightly this month to -36 from -37 in March, below expectations for a reading of -34. The export order book balance rose to -16 from -18, the highest since August 2008. The survey showed firms were continuing to expect to raise prices in the coming months, albeit at a slower pace. “Manufacturing appears to be on an upward trend," said CBI chief economic adviser Ian McCafferty.