#include <bits/stdc++.h>

using namespace std;

int main() {
    int T;
    scanf("%d",&T);
    while (T--) {
        int a,b;
        cin>>a>>b; 
        if (a>b) swap(a,b); 
        if (a==b) {
          if (a==1) {
            puts("-1 -1");
            continue ; 
          }
          cout<<min(2,max(a,b))<<' '<<a<<'\n'; 
          continue ; 
        }
        else {
          int t=b-a;
          if (t==1) {
            cout<<"-1 -1"<<'\n';
            continue ; 
          }
          int mx=t; 
          int mn=t; 
          for (int j=2;j*j<=t;j++) {
            if (t%j==0) {
              mn=j; break ; 
            }
          }
          cout<<mn<<' '<<mx<<'\n'; 
        }
    }
    return 0; 
}