阅读下列程序，写出运行结果:
#include<iostream>
using namespace std;
void func(int a, int b, int c = 3, int d = 4 );
int main()
{
func( 10, 15, 20, 30 );
func( 10, 11, 12 );
func( 12, 12 );
}
void func( int a, int b, int c, int d )
{
cout<<a<<'\t'<<b<<'\t'<<c<<'\t'<<d<< endl;
} 
10 15 20 30
10 11 12 4
12 12 3 4