#include #include double l,v1,v2,v; int n; double f(double t1,double t2) { if(t2-t1<=1e-6) return t1; double time=(t1+t2)/2; if(floor((time*v/l+1)/2.0)+floor((time*(v1+v2)/l+1)/2.0)>=n) return f(t1,time); else return f(time,t2); } int main() { int t; double time,x,dist; scanf("%d",&t); while(t--) { scanf("%lf%lf%lf%d",&l,&v1,&v2,&n); if(v1>v2) v=v1-v2; else v=v2-v1; time=f(0,100000); x=time*v1; while(x>0) x=x-l; dist=(-x)