A sector containing an angle of 240° is cut off from a circle of radius 42 cm and folded into a cone, then the curved surface area of the cone is
4624 cm$^{2}$
3696 cm$^{2}$
6369 cm$^{2}$
6639 cm$^{2}$
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Eight men working 9 hours a day can do a piece of work in 28 days. In how many days will 12 men working for 7 hours a day do the same work?