#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
template<class T>bool chmax(T &a, const T &b) { if (a<b) { a=b; return true; } return false; }
template<class T>bool chmin(T &a, const T &b) { if (b<a) { a=b; return true; } return false; }
#define all(x) (x).begin(),(x).end()
#define fi first
#define se second
#define mp make_pair
#define si(x) int(x.size())
const int mod=998244353,MAX=300005;
const ll INF=1LL<<61;
#pragma GCC optimize("O3,unroll-loops")
#pragma GCC target("avx2,bmi,bmi2,lzcnt,popcnt")

//dynamic CHT MIN

/**
 * 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

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 LineContainerMIN : multiset<Line, less<>> {
    // (for doubles, use inf = 1/.0, div(a,b) = a/b)
    static 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()) return x->p = inf, 0;
        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*=-1;m*=-1;
        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);
    }
};

ll dp[MAX];

int main(){
    
    std::ifstream in("text.txt");
    std::cin.rdbuf(in.rdbuf());
    cin.tie(0);
    ios::sync_with_stdio(false);
    
    int Q;cin>>Q;
    while(Q--){
        ll N,K;cin>>N>>K;
        chmin(K,70LL);
        vector<array<ll,3>> S(N);
        for(int i=0;i<N;i++) cin>>S[i][0];
        for(int i=0;i<N;i++) cin>>S[i][1];
        for(int i=0;i<N;i++) S[i][2]=i;
        sort(all(S));
        int stt=-1,goo=-1;
        for(int i=0;i<N;i++){
            if(S[i][2]==0){
                stt=i;
            }
            if(S[i][2]==N-1){
                goo=i;
            }
        }
        for(int i=0;i<=N;i++){
            dp[i]=INF;
        }
        dp[stt]=0;
        
        for(int t=0;t<=K;t++){
            bool upd=false;
            vector<ll> neL(N,INF),neR(N,INF);
            {
                LineContainerMIN cht;
                for(int i=0;i<N;i++){
                    auto [x,v,iii]=S[i];
                    if(si(cht)) chmin(neR[i],cht.query(x));
                    chmin(neR[i],dp[i]);
                    if(neR[i]!=INF&&neR[i]<dp[goo]) cht.add(v,v*(-x)+neR[i]);
                }
            }
            {
                LineContainerMIN cht;
                for(int i=N-1;i>=0;i--){
                    auto [x,v,iii]=S[i];
                    if(si(cht)) chmin(neL[i],cht.query(-x));
                    chmin(neL[i],dp[i]);
                    if(neL[i]!=INF&&neL[i]<dp[goo]) cht.add(v,v*x+neL[i]);
                }
            }
            for(int i=0;i<N;i++){
                if(min(neL[i],neR[i])<dp[goo]&&chmin(dp[i],min(neL[i],neR[i]))) upd=true;
            }
            if(!upd) break;
        }
        
        cout<<dp[goo]<<"\n";
    }
}