Write the function definition for thecount_afunction called in the following C program. Thecount_afunction counts and returns the number of lettera's in the message entered by the user.

#include

#include

#include

void main()

{

char message[80];

int value;

printf(" Pls enter a message with 25 to 79 characters: ");

gets(message);

value =count_a(message);

printf(" The number of letter a's in the message is: %d", value);

}