#include<iostream>
#include<cmath>
using namespace std;

int main(){
    int t;
    cin>>t;
    while(t--){
        int a,b,flag=1;
        cin>>a>>b;
        if(a==b){
            if(a<=1){
                cout<<-1<<" "<<-1<<endl;
                continue;
            }
            cout<<2<<' '<<a<<endl;
            continue;
        }
        if(a<b){
            int e=a;
            a=b;
            b=e;
        }
        int minn=0,maxn=0;
        int f=sqrt(a),d=a-b;
        for(int i=2;i<=f;i++){
            if(d%i==0){
                minn=i;
                maxn=max(i,d/i);
                flag=0;
                break;
            }
        }
        if(a-b>maxn&&a-b>=2){
            maxn=a-b;
            if(flag){
                minn=a-b;
            }
            flag=0;
        }
        if(flag){
            cout<<-1<<' '<<-1<<endl;
        }
        else{
            cout<<minn<<' '<<maxn<<endl;
        }
    }
    return 0; 
}