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Surface area  =  pi * radius * slant height  +  pi * 8^2  = 

pi * ( 8)  * sqrt (8^2  + 24^2) + pi * 8^2  = 837 m^2

574 pi  =   pi * 29 * slant height       divide through by  29 pi

574/ 29  = 19.79 cm  = 19.8 cm  (rounded )