#include <bits/stdc++.h>

#define N 2006

#define setIO(s) freopen(s".in","r",stdin)

using namespace std;

int p[N],dis[N],z[N],x[N],y[N];

int find(int x)

{

    if(p[x]==x)  return x;

    int rt=find(p[x]);

    dis[x]=dis[x]+dis[p[x]];

    p[x]=rt;

    return rt;

}

void solve()

{

    int n,m,k,i,j;

    scanf("%d%d%d",&n,&m,&k);

    for(i=1;i<=k;++i)  scanf("%d%d%d",&x[i],&y[i],&z[i]),y[i]+=n;

    for(i=1;i<=n+m;++i)   p[i]=i, dis[i]=0;

    for(i=1;i<=k;++i)

    {

        int xx=find(x[i]), yy=find(y[i]);

        if(xx!=yy)

        {

            p[xx]=yy;

            dis[xx]=z[i]+dis[y[i]]-dis[x[i]];

        }

        else if(dis[x[i]]-dis[y[i]]!=z[i])  break;

    }

    if(i>k) printf("Yes\n");

    else printf("No\n");

}

int main()

{

    // setIO("input");

    int T;

    scanf("%d",&T);

    while(T--) solve();

    return 0;

}