#include<bits/stdc++.h>
using namespace std;

int main(){
    int T;
    cin >> T;
    while(T--){
        long long a,b;
        cin >> a >> b;
        long long mmax = -1, mmin = -1;
        if(a == b){
            if(a == 1){
                mmin = -1;
                mmax = -1;
            }
            else{
                mmin = 2;
                mmax = a;
            }
            
        }
        else{
            long long temp = abs(a-b);
            if(temp == 0 || temp == 1){
                mmax = -1;
                mmin = -1;
            }
            else{
                mmax = temp;
                mmin = temp;
            }
            for(int i = 2; i <= sqrt(temp)+1; i++){
                if(temp % i == 0){
                    mmin = i;
                    break;
                }
            }
        }
        cout << mmin << ' ' << mmax << endl;
    }
}