int a[N];
int main() {
    int T;
    cin >> T;
    ll n, k;
    while (T--) {
        int n, k;
        cin >> n >> k;
        k++;
        for (int i = 0; i < n; i++) {
            cin >> a[i];
            int cur = 1;
            while (a[i]--) cur *= 10;
            a[i] = cur;
        }
        ll res = 0;
        for (int i = 0; i < n; i++) {
            int cnt = k;
            if (i + 1 < n) cnt = min(cnt, a[i + 1] / a[i] - 1);
            res += a[i] * 1ll * cnt;
            k -= cnt;
        }
        cout << res << '\n';
    }
    return 0;

    // ll a = (n - base) % k == 0 ? (n - base) / k : (n - base) / k +
    // 1;ll(ceil(1.0*(n-base) / k))
}