초기화에서 float float를 float로 변환 할 수 없습니다.

잘 지내 셨으면 좋겠어요! C ++에서 알아낼 수없는 오류에 대한 도움말을 찾고 있습니다. 저는 C ++의 초보자이며 일반적으로 코딩에 익숙합니다. 이 과제는 오후 11시 59 분에 마감되므로 설명과 함께 답변을 주시면 감사하겠습니다. 모두에게 감사합니다!

오류:

'int main ()'함수에서 : 28 : 7 : 경고 : 사용되지 않은 변수 'totalC'[-Wunused-variable]

함수 'float total_cost (int)': 66:13 : 오류 : 초기화시 'float (*) (float)'를 'float'로 변환 할 수 없습니다.

암호:

#include <iostream>
#include <cmath> 
#include <iomanip>
using namespace std;

//Prototypes:
//Gives user instructions 
void instructions(); 
//Asks user for number of books being bought and downloaded
int prompt();
//Calculation for Sub total without discount 
float calcSubTotal(float);
//Calculation for Discount 
float calcDiscount(int);
//Calculation for Total Cost
float total_cost(int);
//Outputs results for user 
void label(); 


        
int main()
{
instructions();
int nb = prompt(); //save value of prompt as pR
float subT = calcSubTotal(nb); //save value of calcSubTotal as subT
float Disc = calcDiscount(subT); //save value of calcDiscount as Disc
float totalC = total_cost(Disc); //save value of total_cost as totalc
label(); 
return 0;
}

//Instructions  Function 
void instructions(){
cout << "***************************************************************************" << endl; 
cout << " Hello and welcome to BandN Book Store!" << endl; 
cout << " Each eBook costs $8.99." << endl; 
cout << " Today, we are having a special where you can get 15% off your total order. " << endl;
cout << "***************************************************************************" << endl; 
}

//Number of books Function 
int prompt(){
    float books;
    cout << "How many ebooks do you wish to download?" << endl; 
    cin >> books;
return books; 
}

//calcSubTotal Function 
float calcSubTotal(float books){
    float Price_per_book = 8.99; 
    float subTotal = books * Price_per_book;    
return subTotal; 
}

//Discount Function 
float calcDiscount(int Price_Totaldisc){
    float subTotal = Price_Totaldisc;
    float disc = 0.15;  
    float discount = subTotal * disc; 
    float discount_value = subTotal - discount;
return discount_value; 
}

//Total Cost Fucntion
float total_cost(int dis_val){ 
float sub = calcSubTotal; //ERROR
float dis_value = dis_val; 
float totalcost = sub - dis_value; 

    return totalcost; 
}

//Prints Out results 
void label (int nb, float, float subT, float disc, float totalC){ 
    
cout << "***************************************" << endl; 
    cout << "The number of ebooks downloaded: " << nb << endl; 
    cout << setprecision(4); 
    cout << "Sub-total: " << "$" << subT << endl; 
    cout << setprecision(4); 
    cout << "Discount: " << "$" << disc << endl; 
    cout << setprecision(4);
    cout << "Total cost: " << '$' <<  totalC << endl; 
    cout << "***************************************" << endl; 
}