简单的makefile，我的代码如下，怎么make失败呢？，在num.c找不到coun函数

count.h
1 #ifndef COUNT_H
2 #define COUNT_H
3 int coun(int x);
4 #endif

count.c
1 #include“stdio.h”
2 int coun(int x)
3 {return (2*x);
}

num.c
1 #include"stdio.h"
2 #include"count.h"
3 int main()
4 {printf("%d\n",coun(1));
5 }
}
Makefile:
num : num.c count.h
make之后出错