innocent swaps and his emotions

#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
ll mod=pow(10,9) +7;

ll modexp(ll x,ll y)
{
    ll res=1;
    while(y>0)
    {
        if(y%2==1) res=(res*x)%mod;

        y=y/2;
        x=(x*x)%mod;
    }
    return res;
}

ll modinv(ll x)
{
    return (modexp(x,mod-2)+mod)%mod;
}
//O(k)
ll comb(ll n, ll k)
{
    ll res = 1;

    // Since C(n, k) = C(n, n-k)
    if ( k > n - k )
        k = n - k;

    // Calculate value of
    // [n * (n-1) *---* (n-k+1)] / [k * (k-1) *----* 1]
    ll den=1;
    for (ll i = 0; i < k; ++i)
    {
        res = (res*(n - i))%mod;
        den = (den*(i+1))%mod;
    }

    res=(res*modinv(den))%mod;

    return res;
}

int main()
{
    ios_base::sync_with_stdio(0);
    cin.tie(0); cout.tie(0);

    int t; cin>>t;
    while(t--)
    {
        ll n,k; cin>>n>>k;
        ll nCk=comb(n,k);
        ll ans = (nCk*modexp(2,k))%mod;
        cout<<ans<<endl;
    }
}