After merge two array sum of elements in c + +

#include<iostream.h>
#include<conio.h>
class merge
{
private:
int a[10],b[10],c[20],i,sum;
public:
void input();
void rule();
void display();
void add();
};
void merge::input()
{
cout<<"enter the elemnt of 1st array";
for(int i=1;i<=10;i++)
{
cin>>a[i];
}
cout<<"\n enter the element of 2nd array";
for(i=1;i<=10;i++)
{
cin>>b[i];
}
}
void merge::rule()
{
cout<<"\ndata after merge :";
for(int i=1;i<=10;i++)
{
c[i]=a[i];
c[i+10]=b[i];
}}
void merge::display()
{
for(int i=1;i<=20;i++)
{
cout<<c[i]<<" ";
}}
void merge::add()
{
sum=0;
for(int i=1;i<=20;i++)
{
sum=sum+a[i];
}
cout<<"\nData after add:";

cout<<sum<<" ";
}
int main()
{
merge e;
clrscr();
e.input();
e.rule();
e.display();
e.add();
getch();
return 0;
}