[单选题]
A swimmer heading directly ac()ap.qo n) qc*p jolo,ross a river 200 m wide reaches the opposite b/hr-( ibbw+ j; mr mj 72iqp+7kzbs5jvank in 6 min 40 s. Shks27b5mr jwqrbm+p/+b7ziiv(- j j;h e is swept downstream 480 m. How fast can she swim in still water?
