// what is matter? never mind. 
//#pragma GCC optimize("Ofast")
//#pragma GCC optimize("unroll-loops")
//#pragma GCC target("sse,sse2,sse3,sse4,popcnt,abm,mmx,avx,avx2") 
#include<bits/stdc++.h>
#define For(i,a,b) for(int i=(a);i<=(b);++i)
#define Rep(i,a,b) for(int i=(a);i>=(b);--i)
#define ll long long
//#define int long long
#define ull unsigned long long
using namespace std;
inline int read()
{
	char c=getchar();int x=0;bool f=0;
	for(;!isdigit(c);c=getchar())f^=!(c^45);
	for(;isdigit(c);c=getchar())x=(x<<1)+(x<<3)+(c^48);
	if(f)x=-x;return x;
}

#define mod 998244353
struct modint{
	int x;
	modint(int o=0){x=o;}
	modint &operator = (int o){return x=o,*this;}
	modint &operator +=(modint o){return x=x+o.x>=mod?x+o.x-mod:x+o.x,*this;}
	modint &operator -=(modint o){return x=x-o.x<0?x-o.x+mod:x-o.x,*this;}
	modint &operator *=(modint o){return x=1ll*x*o.x%mod,*this;}
	modint &operator ^=(int b){
		modint a=*this,c=1;
		for(;b;b>>=1,a*=a)if(b&1)c*=a;
		return x=c.x,*this;
	}
	modint &operator /=(modint o){return *this *=o^=mod-2;}
	friend modint operator +(modint a,modint b){return a+=b;}
	friend modint operator -(modint a,modint b){return a-=b;}
	friend modint operator *(modint a,modint b){return a*=b;}
	friend modint operator /(modint a,modint b){return a/=b;}
	friend modint operator ^(modint a,int b){return a^=b;}
	friend bool operator ==(modint a,int b){return a.x==b;}
	friend bool operator !=(modint a,int b){return a.x!=b;}
	bool operator ! () {return !x;}
	modint operator - () {return x?mod-x:0;}
	bool operator <(const modint&b)const{return x<b.x;}
};
inline modint qpow(modint x,int y){return x^y;}

vector<modint> fac,ifac,iv;
inline void initC(int n)
{
	if(iv.empty())fac=ifac=iv=vector<modint>(2,1);
	int m=iv.size(); ++n;
	if(m>=n)return;
	iv.resize(n),fac.resize(n),ifac.resize(n);
	For(i,m,n-1){
		iv[i]=iv[mod%i]*(mod-mod/i);
		fac[i]=fac[i-1]*i,ifac[i]=ifac[i-1]*iv[i];
	}
}
inline modint C(int n,int m){
	if(m<0||n<m)return 0;
	return initC(n),fac[n]*ifac[m]*ifac[n-m];
}
inline modint sign(int n){return (n&1)?(mod-1):(1);}

#define fi first
#define se second
#define pb push_back
#define mkp make_pair
typedef pair<int,int>pii;
typedef vector<int>vi;

#define maxn 2000005
#define inf 0x3f3f3f3f

int n,x;
struct seg{
	int l,r;
}a[maxn];

int t[maxn],m;
int cnt[maxn];

struct bit{
	vector<int>tr;
	int n;
	void init(int N){n=N,tr=vector<int>(N+1,0);}
	void add(int x,int y){for(;x<=n;x+=x&-x)tr[x]+=y;}
	int ask(int x){
		int s=0;
		for(;x;x^=x&-x)s+=tr[x];
		return s;
	}
	void down(){For(i,1,n)tr[i]+=tr[i^(i&-i)];}
}tr;

void work()
{
	n=read(),x=read();m=0;
	For(i,1,n)a[i].l=read(),a[i].r=read(),t[++m]=a[i].l;
	sort(a+1,a+n+1,[&](auto x,auto y){
		if(x.r!=y.r)return x.r<y.r;
		return x.l>y.l;
	});
	sort(t+1,t+m+1),m=unique(t+1,t+m+1)-t-1;
	tr.init(m);
	For(i,1,n){
		int pos=lower_bound(t+1,t+m+1,a[i].l)-t;
		pos=m-pos+1;
		cnt[i]=tr.ask(pos),tr.add(pos,1);
	//	cout<<"cnt "<<i<<" "<<cnt[i]<<"\n";
	}
	modint res=0;
	For(i,1,n){
		res+=((a[i].r-a[i].l)%mod)*qpow(2,n-cnt[i]-1);
	}
	res=(qpow(2,n)-1)*(x%mod)-res;
	cout<<res.x<<"\n";
}

signed main()
{
	int T=read();
	while(T--)work();
	return 0;
}
/*

*/