#include<bits/stdc++.h>
#define ll long long
#define fr(i,j,k) for(register int i=j;i<=k;++i)
#define rf(i,j,k) for(register int i=j;i>=k;--i)
#define foredge(i,j) for(register int i=head[j];i;i=e[i].nxt)
#define pb push_back
#define ld long double
#define Times printf("Time:%.3lf\n",clock()/CLOCKS_PER_SEC)
#define pii pair<int,int>
#define mk make_pair
using namespace std;
inline int read(){
	int x=0;
	bool f=0;
	char c=getchar();
	while(!isdigit(c)) f|=(c=='-'),c=getchar();
	while(isdigit(c)) x=(x<<3)+(x<<1)+(c^48),c=getchar();
	return f?-x:x;
}
inline void write(int x){
    if(x<0){putchar('-');x=-x;}
    if(x>9)write(x/10);
    putchar(x%10+'0');
}
inline void writeln(int x){write(x); puts("");}
inline void writepl(int x){write(x); putchar(' ');}
mt19937 rnd(chrono::steady_clock::now().time_since_epoch().count());
inline int randfind(int l,int r){return rnd()%(r-l+1)+l;}
const int Maxn=1e4+10,mod=998244353;
const ld eps=1e-15;
char s[Maxn],c[Maxn];
int trie[Maxn][26],val[Maxn];
int nod=1;
int fail[Maxn];
int sum[Maxn];
inline int getid(char c){return c-'a';}
inline void clear(){
    fr(i,1,nod) fr(j,0,25) trie[i][j]=0;
    fr(i,1,nod) fail[i]=val[i]=sum[i]=0;
    nod=1;
}
inline void ins(int v){
    int ln=strlen(c+1);
    int now=1;
    fr(i,1,ln){
        if(!trie[now][getid(c[i])]) trie[now][getid(c[i])]=++nod;
        now=trie[now][getid(c[i])];
    }val[now]+=v;
}
int n,q;
inline void make_trie(){
    queue<int> q;
    fr(i,0,25){
        if(!trie[1][i]) trie[1][i]=1;
        else fail[trie[1][i]]=1,q.push(trie[1][i]);
    }
    while(!q.empty()){
        int x=q.front();q.pop();
        sum[x]=val[x]+sum[fail[x]];
        fr(i,0,25){
            if(!trie[x][i]) trie[x][i]=trie[fail[x]][i];
            else fail[trie[x][i]]=trie[fail[x]][i],q.push(trie[x][i]);
        }
    }
}
int f[1010][4010],g[1010][4010];
ld db[1010][4010];
inline int ksm(int x,int y=mod-2){
    int sum=1;
    while(y){
        if(y&1) sum=1ll*sum*x%mod;
        y=y/2;x=1ll*x*x%mod;
    }return sum;
}
inline void add(int &x,int y){x+=y;if(x>=mod) x-=mod;}
const ld inf=1e15;
inline bool check(ld x){
    fr(i,0,n) fr(j,0,nod) f[i][j]=g[i][j]=0,db[i][j]=-inf;
    db[0][1]=0;
    // fr(i,0,25) cout<<trie[1][i]<<endl;
    fr(i,1,n){
        fr(j,1,nod) f[i][j]=f[i-1][j],g[i][j]=g[i-1][j],db[i][j]=db[i-1][j];
        int tp=getid(s[i]);
        fr(j,1,nod){
            if(!trie[j][tp]) continue;
            // cout<<j<<' '<<tp<<endl;
            int to=trie[j][tp];
            if(db[i][to]+eps<db[i-1][j]+sum[to]-x){
                // cout<<j<<' '<<to<<endl;
                db[i][to]=db[i-1][j]+sum[to]-x;
                f[i][to]=(f[i-1][j]+sum[to])%mod;
                g[i][to]=(g[i-1][j]+1);
            }
        }
    }
    fr(i,1,nod) if(db[n][i]>0) return true;
    return false;
}
inline void work(){
    n=read();q=read();scanf("%s",s+1);
    clear();
    while(q--){
        scanf("%s",c+1);int x=read();
        ins(x);
    }
    make_trie();
    ld l=0,r=1e9;
    fr(i,0,50){
        ld mid=(l+r)*0.5;
        if(check(mid)) l=mid;
        else r=mid;
    }
    check(l);
    // fr(i,1,nod) cout<<i<<' '<<db[n][i]<<endl;
    fr(i,1,nod) if(db[n][i]>0){
        int ans=1ll*f[n][i]*ksm(g[n][i])%mod;
        writeln(ans);return;
    }
}
inline void init(){
	int t=read();
	while(t--) work();
}
signed main(){
	// freopen("input.in","r",stdin);
	// freopen("output.out","w",stdout);
    init();
    // printf("\nTIME:%.3lf",(double)clock()/CLOCKS_PER_SEC);
	return 0;
}