#include <iostream>
#include <vector>
#include <algorithm>
#include <string.h>
#include <stdio.h>
#include <map>
#include <queue>
using namespace std;
int main()
{
    int n;
    // cin>>n;
    int a, b;
    int x;
    int mx, mn;
    vector<int> v;
    v.push_back(2);
    for (int i = 3; i < 40000; i += 2)
    {
        int len = v.size();
        for (int j = 0; j < len; j++)
        {
            if (v[j] * v[j] > i)
            {
                v.push_back(i);
                break;
            }
            if (i % v[j] == 0)
            {
                break;
            }
        }
    }
    int s[1005][2];
    cin>>n;

        for (int t = 0; t < n; t++)
        {
            scanf("%d %d", &a, &b);

            if (b > a)
            {
                int t = b;
                b = a;
                a = t;
            }
            x = a - b;
            if (a == b)
            {
                x = a;
            }

            mx = x;
            mn = mx;
            int len = v.size();
            for (int i = 0; i < len; i++)
            {
                if (mn % v[i] == 0)
                {
                    mn = v[i];
                    break;
                }
            }
            if (mx == 1)
            {
                mn = -1;
                mx = -1;
            }
            if(a==b && a>=2){
                mn=2;
            }
            printf("%d %d", mn, mx);
            cout<<endl;
        }
    return 0;
}