KINGSTON, Jamaica— World Championship finalists Roshawn Clarke and Sada Williams won the men’s and women’s 400m Open races on Saturday’s 47th staging of the Gibson/McCook Relays held at the National Stadium, both in season’s best times. Clarke the World Under- 20 record holder in the 400m hurdles and who ran on the medal winning Jamaica men’s 4x400m relay team at the World Athletics Championships in Budapest, Hungary last year, equalled his...