probability

#include<bits/stdc++.h>

using namespace std;

#define gc c=getchar()
#define r(x) read(x)
#define ll long long

template<typename T>
inline void read(T&x){
    x=0;T k=1;char gc;
    while(!isdigit(c)){if(c=='-')k=-1;gc;}
    while(isdigit(c)){x=x*10+c-'0';gc;}x*=k;
}

const int N=1e7+7;
const int p=1e9+7;

int fac[N];
int facinv[N];

inline ll qpow(ll a,int b){
    ll ans=1;
    while(b){
        if(b&1)(ans*=a)%=p;
        (a*=a)%=p;
        b>>=1;
    }
    return ans;
}

inline ll inv(ll x){
    return qpow(x,p-2);
}

inline ll calc(ll k,ll n){
    int t1=((k-1)*n+1)/p-(k-1)*(n-1)/p;
    int t2=k*n/p-k*(n-1)/p;
    if(t1^t2)return t1>t2?0:-1;
    ll a=1,b=1;
    for(int t=((k-1)*(n-1)+1)%p,i=1;i<=k;++i){
        if(t)(a*=t)%=p;
        if(++t>=p)t-=p;
    }
    for(int t=(k*(n-1)+1)%p,i=1;i<=k;++i){
        if(t)(b*=t)%=p;
        if(++t>=p)t-=p;
    }
    return a*inv(b)%p*n%p;
}

int main(){
    freopen("probability.in","r",stdin);
    freopen("probability.out","w",stdout);
    fac[0]=1;
    for(int i=1;i<N;++i){
        fac[i]=(ll)fac[i-1]*i%p;
    }
    facinv[N-1]=inv(fac[N-1]);
    for(int i=N-1;i;--i){
        facinv[i-1]=(ll)facinv[i]*i%p;
    }
    int T,k,n;
    for(r(T);T;--T){
        r(k),r(n);
        printf("%lld\n",(ll)k*n<=1e7?((ll)fac[k*(n-1)]*fac[(k-1)*n+1]%p*facinv[(k-1)*(n-1)]%p*facinv[k*n]%p*n%p):calc(k,n));
    }
}