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

typedef long long ll;

pair<bool, ll> isPrime(ll num, ll a, ll b);
ll zmax(ll a, ll b) {
    return a > b ? a : b;
}
ll zmin(ll a, ll b) {
    return a < b ? a : b;
}

int main() {
    /*FILE* stream;
    freopen_s(&stream, "in.txt", "r", stdin);*/

    ll a, b;
    ll amin, amax;
    ll T;
    ios::sync_with_stdio(false);
    cin.tie(0);
    cin >> T;

    while (T--) {
        /*scanf("%d %d", &a, &b);*/
        cin >> a >> b;
        ll dx = a > b ? a - b : b - a;

        if (dx >= 2) {
            amax = dx;
            auto temp = isPrime(dx, a, b);
            if (temp.first) amin = dx;
            else {
                amin = temp.second;
            }
        }
        else if (dx == 1) {
            amax = amin = -1;
        }
        else {
            amax = a;
            amin = 2;
            if (a < 2) {
                amin = amax = -1;
            }
        }
        
        cout << amin << " " << amax << endl;

    }



    return 0;
}

pair<bool, ll> isPrime(ll num, ll a, ll b) {
    ll zx = zmin(zmax(a, b), (ll)sqrt(num));
    for (ll i = 2; i <= zx; ++i) {
        if ((num % i) == 0) return make_pair(false, i);
    }
    return make_pair(true, -1);
}