为什么是mycourses[i]。getGrade()不返回任何内容(C++)?

我遇到了头文件中的getGrade()函数无法根据用户在主文件中输入的标记返回字母等级的问题。当我编译和运行程序时,程序不会根据输入的分数显示字母等级。

头文件(course.h)

#include <iostream>
#include <string>

using namespace std;

class Course {
private:
    int totalMarks;
    char grade;


public:
    void marksInfo(int tm)
    {
        totalMarks = tm;
    }

    int getMarks(void)
    {
        return totalMarks;
    }

    void setGrade(char c)
    {
        if(totalMarks <= 39)
            c = 'E';

        if(totalMarks >= 40 && totalMarks <= 49)
            c = 'D';

        if(totalMarks >= 50 && totalMarks <= 64)
            c = 'C'
    }

    char getGrade(void)
    {
        return grade;
    }
 };

主文件

 #include <iostream>
 #include <string>
 #include "course.h"

 using namespace std;

 int main()
   {
      int tm;

      Course course[5];

      for (int i = 0; i < 5; i++)
      {
          cout << "Subject #" << i+1 << endl;

          cout << "Total Marks #" << i+1 << ": ";
          cin >> tm;

          course[i].marksInfo(tm);

          cout << endl;

          course[i].getGrade();
      }

      cout << "Grade: " << course[0].getGrade();
  }