#include<bits/stdc++.h>
#define debug(x) cerr<<#x<<" = "<<x
#define sp <<"  "
#define el <<endl
#define fgx cerr<<"-----------------------------------"<<endl
#define LL long long
#define ULL unsigned long long
#define pb push_back
using namespace std;
inline LL read(){
    LL nm=0; bool fh=1; char cw=getchar();
    for(;!isdigit(cw);cw=getchar()) fh^=(cw=='-');
    for(;isdigit(cw);cw=getchar()) nm=nm*10+(cw-'0');
    return fh?nm:-nm;
}
#define mod 998244353
namespace  CALC{
    inline int add(int x,int y){return (x+y>=mod)?(x+y-mod):(x+y);}
    inline int mns(int x,int y){return (x-y<0)?(x-y+mod):(x-y);}
    inline int mul(LL x,LL y){return x*y%mod;}
    inline void upd(int &x,int y){x=(x+y>=mod)?(x+y-mod):(x+y);}
    inline void dec(int &x,int y){x=(x-y<0)?(x-y+mod):(x-y);}
    inline int qpow(int x,int sq){LL res=1;for(;sq;sq>>=1,x=mul(x,x))if(sq&1)res=mul(res,x);return res;}
}using namespace CALC;
#define M 100020
int pri[M],tot;
bool isp[M];
inline void solve(){
    LL a=read(),b=read(),num=abs(a-b),cur=-1;
    if(num==0){
        if(a==1) puts("-1 -1");
        else printf("2 %lld\n",a);
        return;
    }
    if(num==1){puts("-1 -1");return;}
    for(int i=1;i<=tot;i++){
        if(num%pri[i]==0){cur=pri[i];break;}
        if(num/pri[i]<pri[i]) break;
    }
    if(cur==-1) cur=num;
    printf("%lld %lld\n",cur,num);
}
int main(){
    memset(isp,true,sizeof(isp)),isp[1]=false;
    for(int i=2;i<M;i++){
        if(isp[i]) pri[++tot]=i;
        for(int j=1;j<=tot;j++){
            if(i*pri[j]>=M) break;
            isp[i*pri[j]]=false;
            if(i%pri[j]==0) break;
        }
    }
    for(int Cas=read();Cas;--Cas) solve();

    return 0;
}