LNK2019 无法解析的外部符号 找不出错误，求大神指导

Question

///zero.h
namespace SALES
{
const int QUARTERS = 4;
struct Sales {
double sales[QUARTERS];
double average;
double max;
double min;
};
void setSales(Sales &s, const double ar[], int n);
void setSales(Sales &s);
void showSales(const Sales &s);
}
////1.cpp
#include
#include"zero.h"
using namespace SALES;

void setSales(Sales &s, const double ar[], int n)
{
double Ave, Max = ar[0], Min = ar[0], Sum = 0;
int i;
for (i = 0; ar[i]!='\0'; i++)
s.sales[i] = ar[i];
while (3 - i > 0)
{
s.sales[i + 1] = 0;
i++;
}
for (int i = 0; ar[i] != '\0'; i++)
if (s.sales[i] > Max)
Max = s.sales[i];
for (int i = 0; ar[i] != '\0'; i++)
if (s.sales[i] < Min)
Min = s.sales[i];
for (int i = 0; ar[i] != '\0'; i++)
Sum += s.sales[i];
Ave = Sum / 4;

}
void setSales(Sales &s)
{

for (int i = 0; i < 4; i++)
{
    using std::cout;
    using std::cin;
    using std::endl;
    cout << "Enter " << i + 1 << " Sales: ";
    cin >> s.sales[i];
}
double Ave, Max = s.sales[0], Min = s.sales[0], Sum = 0;
for (int i = 0;i<4; i++)
    if (s.sales[i] > Max)
        Max = s.sales[i];
for (int i = 0;i<4; i++)
    if (s.sales[i] < Min)
        Min = s.sales[i];
for (int i = 0;i<4; i++)
    Sum += s.sales[i];
Ave = Sum / 4;

}
void showSales(const Sales &s)
{
using std::cout;
using std::endl;
cout << "****************************" << endl;
for (int i = 0; s.sales[i] != '\0'; i++)
cout << i + 1 << " average: " << s.average << " min: " << s.min
<< " max: " << s.max << endl;
}
///2/cpp
#include
#include"zero.h"
using namespace SALES;
int main()
{
double ou[3] = {1,3,5};
Sales dd;
setSales(dd,ou,3);
showSales(dd);
setSales(dd);
showSales(dd);
system("pause");
return 0;
}
严重性 代码 说明 项目 文件 行 禁止显示状态
错误 LNK2019 无法解析的外部符号 "void __cdecl SALES::setSales(struct SALES::Sales &)" (?setSales@SALES@@YAXAAUSales@1@@Z)，该符号在函数 _main 中被引用 ConsoleApplication24 c:\Users\admin\documents\visual studio 2015\Projects\ConsoleApplication24\ConsoleApplication24\2.obj 1

严重性 代码 说明 项目 文件 行 禁止显示状态
错误 LNK2019 无法解析的外部符号 "void __cdecl SALES::setSales(struct SALES::Sales &,double const * const,int)" (?setSales@SALES@@YAXAAUSales@1@QBNH@Z)，该符号在函数 _main 中被引用 ConsoleApplication24 c:\Users\admin\documents\visual studio 2015\Projects\ConsoleApplication24\ConsoleApplication24\2.obj 1

严重性 代码 说明 项目 文件 行 禁止显示状态
错误 LNK2019 无法解析的外部符号 "void __cdecl SALES::showSales(struct SALES::Sales const &)" (?showSales@SALES@@YAXABUSales@1@@Z)，该符号在函数 _main 中被引用 ConsoleApplication24 c:\Users\admin\documents\visual studio 2015\Projects\ConsoleApplication24\ConsoleApplication24\2.obj 1