Need help for my project.

[xhxh00]

1 part of my programme was to check if the booking time is occupied.
anyone can help me with this? what should i do at the end to check if the booking time is occupied?

#include <stdio.h>
void main()
{
	char choice;
	printf("Cyber World Café Booking with F&B Ordering System\n");
    printf("(A) Internet Booking Time Entry\n");
    printf("(B) Internet Booking Time Schedule\n");
    printf("(C) Food and Beverage Ordering\n");
    printf("(D) Calculation and Cash Invoice\n");
    printf("(E) Quit\n");
    printf(" >> Enter Choice:");
    scanf("%c",&choice);

 if(choice == 'a' || choice == 'A')
 {   
	 printf("No of Hours	Exp (PC1)		Std (PC2)		Pro (PC3)\n");
	 printf("1 to 2		$2.99 per hour		$4.99 per hour		$6.99 per hour\n");
	 printf("3 to 5		$1.99 per hour		$3.99 per hour		$5.99 per hour\n");
	 printf("6 to 8		$0.99 per hour		$2.99 per hour		$4.99 per hour\n");
	 printf("9 to 12		$0.49 per hour		$1.99 per hour		$3.99 per hour\n");


	 
	 int in=1;
	 printf("Invoice No: ");
	 scanf("%d",&in);
	 while( in < 1 || in > 99)
	{ printf("Invoice No: ");
	 scanf("%d",&in);
	 }

	 int pcno=1;
	 printf("Pc Station No: ");
	 scanf("%d",&pcno);
	 while(pcno < 1 || pcno > 3)
     {printf("Pc Station No: ");
	 scanf("%d",&pcno);}

	 char name[60];
	 printf("Customer name: ");
	 scanf("%s",&name);
	 

	 int date;
	 printf("Booking date (DD/MM/YYYY): ");
	 scanf("%d",&date);
	 

	 flushall();

	 float timef=900;
	 printf("Booking time from (24hours) :");
	 scanf("%f",&timef);
	 while(timef <900 || timef > 2100)
	 {   printf("***************** [Error Message : Please Re-enter it] *********************** \n");
		 printf("Booking time from (24hours) : ");
	 scanf("%f",&timef);}

	  float timet=900;
	 printf("Booking time to (24hours) : ");
	 scanf("%f",&timet);
     while(timet <900 || timet > 2100 )
	 {   printf("***************** [Error Message : Please Re-enter it] ************************ \n");
		 printf("Booking time to (24hours): ");
	 scanf("%f",&timet);}
	 }