#include <stdio.h>
#include <algorithm>

using std::abs;

void solve(){
    int a,b;
    scanf("%d%d",&a,&b);
    int g = abs(b-a);
    if(a==b){
        if(a==1)
            puts("-1 -1");
        else
            printf("%d %d\n",2,a);
        return;
    }
    int f = g;
    for(int i=2;i*i<=g;i++)
        if(g%i==0){
            f = i;
            break;
        }
    if(g==1){
        puts("-1 -1");
    }else{
        printf("%d %d\n",f,g);
    }
}

int main(){
    int T;
    scanf("%d",&T);
    while(T--) solve();
}