#include <cmath>
#include <iostream>
using namespace std;
void solve() {
    int a, b;
    cin >> a >> b;
    if (a == b) {
        if (a == 1)
            cout << "-1 -1\n";
        else
            cout << "2 " << a << "\n";
    } else {
        if (a < b) swap(a, b);
        int mx = a - b;
        if (mx < 2) {
            cout << "-1 -1\n";
            return;
        }
        int mn;
        int sq = sqrt(mx);
        for (mn = 2; mn <= sq; mn++) {
            if (mx % mn == 0) {
                break;
            }
        }
        if (mn > sq) {
            mn = mx;
        }
        cout << mn << " " << mx << "\n";
    }
}
int main() {
    int T;
    cin >> T;
    while (T--) solve();
    return 0;
}