#include<stdio.h>
#include<conio.h>

const int SauCung = -1;
const int GioiHan[] = { 0, 100, 150, 200, 300, SauCung };
int nGioiHan = sizeof(GioiHan) / sizeof(GioiHan[0]);

const double Gia[] = { 550, 900, 1250, 1450, 1700 };
int nGia = sizeof(Gia) / sizeof(Gia[0]);

static const double VAT_rate = 0.1;

double TinhTungKhoang(int GioiHan1, int GioiHan2, double Gia, int kWh)
{
	double GiaTri = 0;
	if (kWh >= GioiHan1)
	{
		if (kWh < GioiHan2 || GioiHan2 == SauCung)
		{
			GiaTri = (kWh - GioiHan1) * Gia;
		}
		else
		{
			GiaTri = (GioiHan2 - GioiHan1) * Gia;
		}
	}
	return GiaTri;
}
double TienDien(int kWh)
{
	double TongTien = 0;
	for (int i = 0; i < nGioiHan - 1; i++)
	{
		TongTien += TinhTungKhoang(GioiHan[i], GioiHan[i + 1], Gia[i], kWh);
	}
	// Tính thuế VAT
	TongTien = (1 + VAT_rate) * TongTien;
	return TongTien;
}
int main()
{
	int kWh;
	printf("\nNhap so kWh nha anh Son tieu thu trong thang:))->> ");
	scanf_s("%d", &kWh);
	double TongTien = TienDien(kWh);
	printf("\nTong so tien anh Son phai thanh toan la: %.0f VND\n", TongTien);


	_getch();
	return 0;
}

Line 17: error: conio.h: No such file or directory
Line 5: error: initializer element is not constant
Line 5: error: (near initialization for 'GioiHan[5]')
In function 'TienDien':
Line 32: error: 'for' loop initial declaration used outside C99 mode