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#include <algorithm>
#include <bitset>
#include <iostream>
#include <list>
#include <map>
#include <queue>
#include <set>
#include <string>
#include <vector>

using namespace std;

#define PB pusumHalf_back
#define MP make_pair
#define F first
#define S second
#define ALL(x) (x).begin(),(x).end()
#define SIZE(x) (int)(x).size()
#define CLEAR(tab) memset(tab, 0, sizeof(tab))
#define REP(x, n) for(int x = 0; x < (n); x++)
#define FOR(x, b, e) for(int x = (b); x <= (e); x++)
#define FORD(x, b, e) for(int x = (b); x >= (e); x--)
#define VAR(v, n) __typeof(n) v = (n)
#define FOREACH(i, c) for(VAR(i, (c).begin()); i != (c).end(); ++i)
#define DEBUG(fmt, ...) fprintf(stderr, fmt, ##__VA_ARGS__)

typedef long long int LL;
typedef pair<int,int> PII;
typedef vector<int> VI;

const int MXN = 40000010;
const int INF = 1000000001;
const int MOD = 1000000007;

int n;
LL fac[MXN], fac_inv[MXN], INV2, INV3, is_maxi[MXN];

LL pow(LL a, LL b) {
	LL res = 1;
	a %= MOD;

	while(b)  {
		if(b % 2)
			res = res * a % MOD;
		a = a * a % MOD;
		b /= 2;
	}

	return res;
}

void init(int m) {
	fac[0] = 1;
	FOR(i, 1, m)
		fac[i] = fac[i - 1] * i % MOD;
	fac_inv[m] = pow(fac[m], MOD - 2);
	FORD(i, m - 1, 0)
		fac_inv[i] = fac_inv[i + 1] * (i + 1) % MOD;
	INV2 = pow(2, MOD - 2);
	INV3 = pow(3, MOD - 2);
}

LL C(int n, int k) {
	return ((fac[n] * fac_inv[k] % MOD) * fac_inv[n - k] % MOD);
}

LL calc_3(int n, int k) {
	return ((8LL * k % MOD * n % MOD) + (5LL * k % MOD * k % MOD) - (28LL * k % MOD) + 18 + MOD) % MOD;
}

LL calc2(int n, int k, LL sumHalf, LL sumHalfSquared) {
	LL sq = (2 * n - k + MOD) % MOD;
	sq = sq * sq % MOD;
	LL t1 = pow(2, k - 1) * ((2 * k - 1) % MOD) % MOD * sq % MOD;
	LL t2 = calc_3(n, k) * sumHalf % MOD;
	LL t3 = k * sumHalfSquared % MOD;
	return (t1 + t2 - t3 + MOD) % MOD;
}

LL calc(int n, int k) {
	return fac[4 * n - 2 * k - 2] * pow(INV2, 2 * n - k - 1) % MOD;
}


void test() {
	int n;
	scanf("%d", &n);
	init(4 * n + 1);
	int n2 = 2 * n;
	vector<int> a(n2);
	FOR(i, 0, n2 - 1)
		scanf("%d", &a[i]);

	int mini = a[0];
	int maxi = a[0];
	FOR(i, 1, n2 - 1) {
		mini = min(mini, a[i]);
		maxi = max(maxi, a[i]);
	}
	if(maxi - mini > 1) {
		printf("0\n");
		return;
	}

	int S = 0;
	FOR(i, 0, n - 1) {
		int L = a[2 * i] - a[(2*i + 1) % n2];
		int R = a[(2 * i + 2) % n2] - a[(2 * i + 1) % n2];
		if(min(L, R) < 0 || max(L, R) > 1) {
			printf("0\n");
			return;
		}
		S += L;
	}

	if(S == 0) {
		LL P = 0;
		if(mini == 1)
			P = 2 * n * n;
		else
			P = n * (2 * n - 1);
		printf("%lld\n", calc(n, 0) * P % MOD);
		return;
	}

	vector<int> t;
	FOR(i, 0, n2 - 1)
		is_maxi[i] = (a[i] == maxi);
	FOR(i, 0, n2 - 1)
		if(is_maxi[i] != is_maxi[(i + 1) % n2])
			t.push_back(i);
	LL sumHalf = 0, sumHalfSquared = 0;
	FOR(i, 0, SIZE(t) - 1) {
		int s0 = (t[i] + 1) % n2;
		int s1 = t[(i + 1) % t.size()];
		int len = (s1 - s0 + 1 + n2) % n2;
		if(!len)
			len = n2;
		if((mini == 0 && is_maxi[s0]) || (mini && !is_maxi[s0]) ) {
			int h = (len - 1) / 2;
			sumHalf = (sumHalf + h) % MOD;
			sumHalfSquared = (sumHalfSquared + (LL) h * h) % MOD;
		}
	}

	printf("%lld\n", calc(n, S) * calc2(n, S, sumHalf, sumHalfSquared) % MOD);
}

int main() {
	int te = 1;
	scanf("%d", &te);
	while(te--)
		test();
	return 0;
}