#include<iostream>
#include<cstring>
#include<map>
#include<vector>


using namespace std;


long long a, b, t;

int main() {
    cin >> t;
    while (t--) {
        cin >> a >> b;
        if (b == a) {
            if (1 == a) {
                cout << "-1 -1\n";
            } else {
                cout << "2 " << a << '\n';
            }
        } else {
            long long ans2 = max(a, b) - min(a, b);
            if (1 >= ans2) {
                cout << "-1 -1\n";
            } else {
                long long ans1 = ans2;
                vector<long long> res;
                long long n = ans2;
                for (long long i = 1; i * i <= n; ++i) {
                    if (n % i == 0) {
                        res.push_back(i);
                        if (n / i != i) {
                            res.push_back(n / i);
                        }
                    }
                }
                for (auto it : res) {
                    if (it > 1) {
                        ans1 = min(ans1, it);
                    }
                }
                cout << ans1 << ' ' << ans2 << '\n';
            }
        }
    }
    return 0;
}