#include <iostream>

using namespace std;

typedef long long ll;

ll a[110];

ll n, h;

bool check(ll k)

{

    ll t = h - k;

    for (int i = 2; i <= n; ++i)

    {

        t -= min(k, a[i] - a[i - 1]);

    }

    if (t <= 0)

        return 1;

    else

        return 0;

}

int main()

{

    ios::sync_with_stdio(false);

    cin.tie(0);

    cout.tie(0);

    int T;

    cin >> T;

    while (T--)

    {

        cin >> n >> h;

        for (int i = 1; i <= n; ++i)

        {

            cin >> a[i];

        }

        ll l = 1, r = h;

        while (l <= r)

        {

            ll mid = (l + r) >> 1;//取中点

            if (check(mid))

            {

                r = mid - 1;

            }

            else

                l = mid + 1;

        }

        cout << l << endl;

    }

    return 0;

}