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#1 4:40
By 4:40, the cutters had finished their work. -
#2 4:43
At 4:43, someone lit a cigarette and put it in the bucket. -
#3 4:45
at exactly 4:45, someone pulled the 8th floor fire alarm. -
#4 4:49
At 4:49, people were racing to the elevators and emergency stairs.