[单选题]
A 60-kg skier starts from rest fro*u4akb ;lvwofgnt9sqp(5 5y*hwt6g;m the top of a 50-m high slop4zfe(* i5qghke. If the work done by frigqi 4e5(z*fkhction is $-6.0 \times 10^{3} \; J$, what is the speed of the skier on reaching the bottom of the slope?