求助新人求助，纠结好几天，还是没想到怎么改，程序运行错误

float p,w,f;
int d,s;
printf("请输入数据:\n");
scanf("%f %f %f",&p,&w,&s);
f=p*w*s*(1-d/100.0);
switch(s)
{
case s<250:
d==0;
printf("%f",f);
break;
case s>=250&&s<500:
d==2;
printf("%f",f);
break;
case s>=500&&s<1000:
d==5;
printf("%f",f);
break;
case s>=1000&&s<2000:
d==8;
printf("%f",f);
break;
case s>=2000&&s<3000:
d==10;
printf("%f",f);
break;
case s>=3000:
d==15;
printf("%f",f);
break;
default:
printf("错误");
break;
}
return 0;
}