/*
 * Author: Kewth

 * Date:
  echo -n '  ' && date +%Y.%m.%d # Type "!!sh" in Vim.

 * Solution:
  To be updated after "Accept".

 * Digression:

 * CopyRight:
   __  __                  __   __
  |  |/  |.-----.--.--.--.|  |_|  |--.
  |     < |  -__|  |  |  ||   _|     |
  |__|\__||_____|________||____|__|__|

 */

#include <cstdio>
#include <algorithm>
#define debug(...) fprintf(stderr, __VA_ARGS__)

typedef long long ll;

static struct {
    inline operator int () { int x; return scanf("%d", &x), x; }
    /* inline operator ll () { ll x; return scanf("%lld", &x), x; } */
    /* template<class T> inline void operator () (T &x) { x = *this; } */
    /* template<class T, class ...A> inline void operator () (T &x, A &...a) */
    /* { x = *this; this -> operator () (a...); } */
} read;

int main () {
    int q = read;
    while (q --) {
        int a = read, b = read;
        a -= b;
        if (a < 0) a = -a;
        if (a == 0) {
            if (b == 1)
                puts("-1 -1");
            else
                printf("%d %d\n", 2, b);
            goto END;
        }
        for (int x = 2; x <= a / x; x ++)
            if (a % x == 0) {
                printf("%d %d\n", x, a);
                goto END;
            }
        if (a == 1)
            puts("-1 -1");
        else
            printf("%d %d\n", a, a);
END:;
    }
}