Concept:Let the planned daily output be x pieces. The time is found by comparing the planned time with the actual time at the increased rate.Explanation:Planned number of days =x360​.New daily output =x+4 pieces.New number of days =x+4360​.Since the work is completed 1 day earlier, we write:x360​−x+4360​=1Solving:x(x+4)360(x+4)−360x​=1x(x+4)1440​=1x2+4x−1440=0x2+40x−36x−1440=0(x+40)(x−36)=0So, x=36 pieces per day, since x=−40 is not possible.New daily output =36+4=40 pieces.Days required under the new planning:40360​=9 daysAnswer:Option B. 9 days.