2.4

#include <iostream>
#include <vector>

using namespace std;
int main() {
    vector<int> vec;
    cout << "Real size of array in vector: " << vec.capacity() << endl;
    for (int j = 0; j < 25; j  ) {
        vec.push_back(10);
    }
    cout << "Real size of array in vector: " << vec.capacity() << endl;
    system("pause");
    return 0;
}
Run on cpp.sh