#include <bits/stdc++.h>

using namespace std;
#define int long long
#define app push_back
#define all(x) (x).begin(),(x).end()
#ifdef LOCAL
#define debug(...) [](auto...a){ ((cout << a << ' '), ...) << endl;}(#__VA_ARGS__, ":", __VA_ARGS__)
#else
#define debug(...)
#endif
#ifdef LOCAL
#define __int128 long long
#endif // LOCAL
const int inf=1e18;
/**
 * Author: Simon Lindholm
 * Date: 2017-04-20
 * License: CC0
 * Source: own work
 * Description: Container where you can add lines of the form kx+m, and query ///maximum values at points x.
 *  Useful for dynamic programming (``convex hull trick'').
 * Time: O(\log N)
 * Status: stress-tested
 */
#pragma once
#define ll long long
struct Line {
    mutable ll k, m, p;
    bool operator<(const Line& o) const { return k < o.k; }
    bool operator<(ll x) const { return p < x; }
};

struct LineContainer : multiset<Line, less<>> {
    // (for doubles, use inf = 1/.0, div(a,b) = a/b)
    const ll inf = LLONG_MAX;
    ll div(ll a, ll b) { // floored division
        return a / b - ((a ^ b) < 0 && a % b); }
    bool isect(iterator x, iterator y) {
        if (y == end()) { x->p = inf; return false; }
        if (x->k == y->k) x->p = x->m > y->m ? inf : -inf;
        else x->p = div(y->m - x->m, x->k - y->k);
        return x->p >= y->p;
    }
    void add(ll k, ll m) {
        k=(-k);m=(-m);
        auto z = insert({k, m, 0}), y = z++, x = y;
        while (isect(y, z)) z = erase(z);
        if (x != begin() && isect(--x, y)) isect(x, y = erase(y));
        while ((y = x) != begin() && (--x)->p >= y->p)
            isect(x, erase(y));
    }
    ll query(ll x) {
        assert(!empty());
        auto l = *lower_bound(x);
        return -(l.k * x + l.m);
    }
};
int32_t main()
{
    ios_base::sync_with_stdio(false);cin.tie(0);cout.tie(0);
    int t;cin>>t;
    while(t--)
    {
        int n,k;cin>>n>>k;k=min(k,20LL);
        vector<array<int,3> > a(n);
        for(int i=0;i<n;++i) {cin>>a[i][1];} for(int i=0;i<n;++i) {cin>>a[i][0];} for(int i=0;i<n;++i) {a[i][2]=i;}
        sort(all(a),[&](array<int,3> u,array<int,3> v) {return u[1]<v[1];});int pos=0;while(a[pos][2]) {++pos;}
        int pos2=0;while(a[pos2][2]!=(n-1)) {++pos2;}
        vector<int> dp(n);fill(all(dp),inf);dp[pos]=0;
        for(int i=0;i<=k+1;++i)
        {
            LineContainer l1;
            for(int j=pos;j>=0;--j)
            {
                l1.add(-a[j][0],a[j][0]*a[j][1]+dp[j]);
                dp[j]=min(dp[j],l1.query(a[j][1]));
            }
            LineContainer l2;
            for(int j=pos;j<n;++j)
            {
                l2.add(a[j][0],-a[j][0]*a[j][1]+dp[j]);
                dp[j]=min(dp[j],l2.query(a[j][1]));
            }
            vector<int> dp2=dp;
            if(i<=k)
            {
                LineContainer l1;
                for(int j=n-1;j>=0;--j)
                {
                l1.add(-a[j][0],a[j][0]*a[j][1]+dp[j]);
                dp2[j]=min(dp[j],l1.query(a[j][1]));
                }
                LineContainer l2;
                for(int j=0;j<n;++j)
                {
                l2.add(a[j][0],-a[j][0]*a[j][1]+dp[j]);
                dp2[j]=min(dp[j],l2.query(a[j][1]));
                }
                dp=dp2;
            }
        }
        cout<<dp[pos2]<<'\n';
    }
    return 0;
}