first AND last name output with grades

on line 28 and 29 i do not understand the errors i am getting

main.cpp:28: error: conversion from 'std::string*' to non-scalar type 'std::string' requested
main.cpp:29: error: conversion from 'std::string*' to non-scalar type 'std::string' requested

i am taking first and last names from a file and 10 grades and then finding the average and then outputting it to the window. no sorting or anything complicated but i do not why i get that error and what i can do to fix it

Here is my program

#include<iostream>
#include<fstream>
#include<iomanip>
#include<string>


using namespace std;

const int NUM_GRADES=10; ////Total grades
const int NUM_STUDENTS=10; //Total Number of Students


void gData(string firstName[], string lastName[], int grades [][NUM_GRADES]); //Function to read from input file.
void CompAvg(string firstName, string lastName, int grades [][NUM_GRADES], float avgs []); //calculate average of each student.
void printData(string firstName, string lastName, int grades [][NUM_GRADES], float avgs []); //Function to display the result.

int main()
{
    //string names [NUM_STUDENTS];
    string firstName[NUM_STUDENTS], lastName[NUM_STUDENTS];
    
    int grades [NUM_STUDENTS][NUM_GRADES];
    float avgs [NUM_STUDENTS];
    
    
    //Calling functions
    gData(firstName, lastName,grades);
    CompAvg(firstName, lastName, grades, avgs);
    printData(firstName, lastName, grades, avgs);

    
    
    
    return 0;
}

void gData(string firstName [],string lastName [], int grades [][NUM_GRADES])//(string names, int grades)
{
    string filename;
    ifstream fin;
    cout<<"Enter filename: "; //User required to enter file name
    cin>>filename;
    fin.open (filename.c_str());
    while(!fin) {
      cerr<<"Error: Please enter a valid file name.\n";
      cout << "Enter filename: ";
      cin >> filename;
      fin.open (filename.c_str());
    }
    
    
    
    
    for (int i=0;i <= NUM_STUDENTS; ++i)
    {
      fin >> firstName[i] >> lastName[i];
      
      for (int j=0;j<=NUM_GRADES; ++j)
      {
        fin >> grades [i][j];
        
      }
    }
    fin.close();
}

void CompAvg(string firstName [], string lastName [], int grades [][NUM_GRADES], float avgs [])//(int grades, float average)
{
    float total = 0; //To hold an average temporarily
    ifstream fin;
    for(int i=0;i<NUM_GRADES; ++i)
    {
        fin >> firstName[i] >> lastName[i];
        for(int j=0;j<NUM_GRADES; ++j)
        {
            fin >> grades [i][j];
            total += grades[i][j]; //Adding up all the grades
        }

    avgs [i] = total /NUM_GRADES;
    }
}




void printData(string firstName[], string lastName[], int grades[][NUM_GRADES], float avgs[])
{
    // output table
    cout<<"Name\t\t\t\t\t\t"<<"Grades\t\t\t\t\t"<<"Average\n\n";
    
    for(int i=0;i<NUM_STUDENTS;++i)
    {
        cout<<firstName[i] << lastName[i];//Display name
       
        for(int j=0;j<NUM_GRADES;++j)
        {
            cout<<grades[i][j]; //Display 10 grades
        }
       //cout<<fixed<<setprecision(2)<<"\t"<<names[i]<<"\n"; //Display Grades
    }
}