#include<bits/stdc++.h>
#define endl '\n'
#define int long long
#define double long double
using namespace std;
constexpr int N=1e10+10;
constexpr int mod=998244351;
void solve()
{
    int n,m;
    cin >> n >> m;
    m++;
    vector<int> f(n);
    for(int i=0;i<n;i++)
    {
        cin >> f[i];
        int num=1;
        for(int j=f[i];j>0;j--)
        {
            num*=10;
        }

        f[i]=num;
    }
    int ans=0;
    int tmp=0;
    for(int i=0;i<n-1;i++)
    {
        int num=f[i+1]/f[i]-1;
        if(m>=num)
        {
            m-=num;
            ans+=num*f[i];
        }else 
        {
            cout << ans+m*f[i] << endl;
            return;
        }
    }
    if(m)
    {
        ans+=m*f[n-1];
        cout << ans << endl;
    }
}
signed main()
{
    std::ios::sync_with_stdio(false);
    std::cin.tie(nullptr);

    int o;
    cin >> o;
    while(o--)
    solve();
    return 0;
}
//
//⠀⠀⠀             ⠀⢸⣿⣿⣿⠀⣼⣿⣿⣦⡀
//⠀⠀⠀⠀⠀⠀⠀⠀⠀⣀⠀⠀⠀ ⠀⢸⣿⣿⡟⢰⣿⣿⣿⠟⠁
//⠀⠀⠀⠀⠀⠀⠀⢰⣿⠿⢿⣦⣀⠀⠘⠛⠛⠃⠸⠿⠟⣫⣴⣶⣾⡆
//⠀⠀⠀⠀⠀⠀⠀⠸⣿⡀⠀⠉⢿⣦⡀⠀⠀⠀⠀⠀⠀ ⠛⠿⠿⣿⠃
//⠀⠀⠀⠀⠀⠀⠀⠀⠙⢿⣦⠀⠀⠹⣿⣶⡾⠛⠛⢷⣦⣄⠀
//⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⣿⣧⠀⠀⠈⠉⣀⡀⠀ ⠀⠙⢿⡇
//⠀⠀⠀⠀⠀⠀⢀⣠⣴⡿⠟⠋⠀⠀⢠⣾⠟⠃⠀⠀⠀⢸⣿⡆
//⠀⠀⠀⢀⣠⣶⡿⠛⠉⠀⠀⠀⠀⠀⣾⡇⠀⠀⠀⠀⠀⢸⣿⠇
//⢀⣠⣾⠿⠛⠁⠀⠀⠀⠀⠀⠀⠀⢀⣼⣧⣀⠀⠀⠀⢀⣼⠇
//⠈⠋⠁⠀⠀⠀⠀⠀⠀⠀⠀⢀⣴⡿⠋⠙⠛⠛⠛⠛⠛⠁
//⠀⠀⠀⠀⠀⠀⠀⠀⠀⣀⣾⡿⠋⠀
//⠀⠀⠀⠀⠀⠀⠀⠀⢾⠿⠋⠀
//