#include <iostream>
#include <cstdio>
#include <cstring>
#include <map>
#include <set>
#include <algorithm>
#include <cmath>
#include <cstdlib>
#include <queue>
 
#define X first
#define Y second
#define PB push_back
#define MP make_pair
#define EB emplace_back
#define mset(var,val) memset(var,val,sizeof(var))
#define IOS ios::sync_with_stdio(false);cin.tie(0)
 
#define rep(i,n) for(int i = 0; i < n; ++i)
#define rep1(i,n) for(int i = 1; i <= n; ++i)
 
using namespace std;
typedef long long ll;
 
#ifdef local
#define dbg(args...) do { cout << #args << " -> "; err(args); } while (0)
void err() {
    cout << endl;
}
template<template<typename...> class T, typename t, typename... Args>
void err(T<t> a, Args... args) {
    for (auto x: a)
        cout << x << ' ';
    err(args...);
}
template<typename T, typename... Args>
void err(T a, Args... args) {
    cout << a << ' ';
    err(args...);
}
#else
#define dbg(...)
#endif
typedef pair<int,int> pii;
const int inf = 0x3f3f3f3f;
const long long INF = 0x3f3f3f3f3f3f3f3fLL;
const double PI = acos(-1.0);
const double eps = 1e-8;
//const int mod=1e9+7;
const int N = 1e5+5;
const int M = N*100;
const int maxn=1e7+50;

ll gcd(ll a, ll b) {
    return a%b?gcd(b,a%b):b;
}

void work() {
    ll a,b;
    cin >> a >> b;
    if (a < b) swap(a,b);
    if (a == b) {
        if (a == 1) {
            cout << -1 << " " << -1 << "\n";
            return;
        }
        cout << 2 << " " << max(a,2ll) << "\n";
        return;
    }
    ll x = a - b;
    if (x != 1) {
        ll y = x;
        for (ll i = 2; i <= sqrt(x+1); ++i) {
            if (x%i==0) {
                y = i;
                break;
            }
        }
        cout << y << " " << x << "\n";
    } else {
        cout << -1 << " " << -1 << "\n";
    }
    
}
 
int main() {
#ifdef local
    freopen("in.txt","r",stdin);
//    freopen("out.txt","w",stdout);
#endif // local
    IOS;
//    init();
     int t;
     cin>>t;
     while(t--)
        work();
    return 0;
}