#include <iostream>
#include <algorithm>

using namespace std;

int main()
{
    int t;
    cin >> t;
    while(t--) {
        int a, b;
        cin >> a >> b;
        if(a == b) {
            if(a > 1) {
                cout << "2 " << a << endl;
                continue;
            }
        }
        int d = max(a, b) - min(a, b);
        if(d < 2) {
            cout << "-1 -1\n";
            continue;
        }
        int r1 = d, r2 = d;
        for(int c = 2; c * c <= d; c++) {
            if(d % c == 0) {
                r1 = c;
                break;
            }
        }
        cout << r1 << ' ' << r2 << endl;
    }
    return 0;
}