#include <iostream>
#include <stdio.h>
#include <math.h>
using namespace std;
typedef long long llong;

llong eval(llong b,llong c,llong x)
{
    return x*x + b*x + c;
}

llong getSmallerOrEq(llong b,llong c,llong s,llong v)
{
    if (4LL * (c - v) > b*b)
        return 0LL;

    long double cs= sqrt( (long double)( b*b - 4LL * (c - v) ) );
    llong approx = (-b + (llong)cs)/2LL;

    while(eval(b,c,approx) <= v)
        approx++;

    while(eval(b,c,approx) > v)
        approx--;


    if (approx < s)
        return 0;

    return approx - s + 1;
}

int main()
{
    freopen("sequences.in","r",stdin);
    freopen("sequences.out","w",stdout);

    int q;
    int i;

    scanf("%d",&q);

    for (i=1;i<=q;i++)
    {
        llong b1,c1,s1;
        llong b2,c2,s2;
        llong n;

        llong l = -4000000000000000000, r = 4000000000000000000;
        llong mid,best;

        scanf("%lld %lld %lld %lld %lld %lld %lld",&b1,&c1,&s1,&b2,&c2,&s2,&n);

        while(l <= r)
        {
            mid = (l + r) / 2LL;

            llong cnt = getSmallerOrEq(b1, c1, s1, mid) + getSmallerOrEq(b2, c2, s2, mid);

            if (cnt >= n)
            {
                best = mid;
                r = mid - 1LL;
            }
            else
            {
                l = mid + 1LL;
            }
        }

        printf("%lld\n",best);
    }

    return 0;
}