阶梯电价问题一直通不过，想问一下错在了哪里

#include
using namespace std;

int main()
{
int d,y;
cin>>d;
if(0<=d&&d<=240)
{y=0.4883d;
printf("%.2lf",y);
}
else if(240<d&&d<=400)
{y=0.4883*240+(d-240)*0.5383;
printf("%.2lf",y);
}
else if(d>400)
{y=2400.4883+160*0.5383+(d-400)*0.7883;
printf("%.2lf",y);
}

return 0;

}
谢谢

整形的y改成浮点型 double y;