#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define pb push_back
#define mp make_pair
#define ALL(x) (x).begin(),(x).end()
#define rALL(x) (x).rbegin(),(x).rend()
#define srt(x) sort(ALL(x))
#define rev(x) reverse(ALL(x))
#define rsrt(x) sort(rALL(x))
#define sz(x) (int)(x.size())
void die(string S){puts(S.c_str());exit(0);}
int main()
{
    int t;
    cin>>t;
    while(t--)
    {
        ll a,b;
        cin>>a>>b;
        if(a==b)
        {
            if(a==1)
                cout<<"-1 -1\n";
            else    cout<<2<<" "<<a<<endl;
            continue;
        }
        if(a<b)
            swap(a,b);
        ll x=a-b;
        ll y=x;
        for(int i=2;i<100000;i++)
            if(x%i==0)
            {
                y=i;
                break;
            }
        if(x==1)
            puts("-1 -1");
        else    cout<<y<<" "<<x<<endl;
    }
    return 0;
}