#include <bits/stdc++.h>
using namespace std;
#define rep(i,a,n) for (int i=a;i<n;i++)
#define per(i,a,n) for (int i=n-1;i>=a;i--)
#define pb push_back
#define mp make_pair
#define all(x) (x).begin(),(x).end()
#define fi first
#define se second
#define SZ(x) ((int)(x).size())
typedef vector<int> VI;
typedef long long ll;
typedef pair<int,int> PII;
typedef double db;
mt19937 mrand(random_device{}());
const ll mod=1000000007;
int rnd(int x) { return mrand() % x;}
ll powmod(ll a,ll b) {ll res=1;a%=mod; assert(b>=0); for(;b;b>>=1){if(b&1)res=res*a%mod;a=a*a%mod;}return res;}
ll gcd(ll a,ll b) { return b?gcd(b,a%b):a;}
// head

int main() {
    int T;
    scanf("%d", &T);
    while(T--) {
        int a, b;
        scanf("%d%d", &a, &b);
        int d = max(a, b)-min(a, b);
        if(d==0) {
            if(a==1)
                printf("-1 -1\n");
            else
                printf("2 %d\n", a);
            continue;
        }
        if(d==1) {
            printf("-1 -1\n");
            continue;
        }
        int mn = 0;
        for(int i=2; i*i<=d; i++) {
            if(d%i==0) {
                mn = i;
                break;
            }
        }
        if(!mn)
            mn = d;
        printf("%d %d\n", mn, d);
    }
    return 0;
}