What will be the output of the following C++ code?

#include <iostream>
using namespace std;
class BaseClass 
{
    int i;
    public:
    void setInt(int n);
    int getInt();
};
class DerivedClass : public BaseClass
{
    int j;
    public:
    void setJ(int n);
    int mul();
};
void BaseClass::setInt(int n)
{
    i = n;
}
int BaseClass::getInt()
{
    return i;
}
void DerivedClass::setJ(int n)
{
    j = n;
}
int DerivedClass::mul()
{
    return j * getInt();
}
int main()
{
    DerivedClass ob;
    ob.setInt(10);       
    ob.setJ(4);          
    cout << ob.mul();    
    return 0;
}

A. 10

B. 4

C. 40

D. 30

Answer: Option C