Read this: The military effectiveness of bombing varied. The Luftwaffe dropped around 45,000 short tons (41,000 t) of bombs during the Blitz disrupting production and transport, reducing food supplies and shaking the British morale. It also helped to support the U-Boat blockade by sinking some 58,000 long tons (59,000 t) of shipping destroyed and 450,000 long tons (460,000 t) damaged. Yet, overall the British production rose steadily throughout this period although there were significant falls during April 1941, probably influenced by the departure of workers of Easter Holidays according to the British official history. The British official history on war production noted the great impact was upon the supply of components rather than complete equipment. In aircraft production, the British were denied the opportunity to reach the planned target of 2,500 aircraft in a month, arguably the greatest achievement of the bombing, as it forced the dispersal of industry. In April 1941, when the targets were British ports, rifle production fell by 25%, filled-shell production by 4.6%, and in smallarms production 4.5% overall. The strategic impact on industrial cities was varied; most took from 10–15 days to recover from heavy raids, although Belfast and Liverpool took longer. The attacks against Birmingham took war industries some three months to recover fully from. The exhausted population took three weeks to overcome the effects of an attack.

How long was the recovery of industrial cities from raids?
What is the answer? (If it cannot be answered, return "unanswerable")
most took from 10–15 days