#include <iostream>
#include <cstdio>
#include <vector>
#include <algorithm>
#include <complex>
#include <cstring>
#include <cstdlib>
#include <string>
#include <cmath>
#include <cassert>
#include <queue>
#include <set>
#include <map>
#include <valarray>
#include <bitset>
#include <stack>
using namespace std;

#define REP(i,n) for(int i=0;i<(int)n;++i)
#define FOR(i,c) for(__typeof((c).begin())i=(c).begin();i!=(c).end();++i)
#define ALL(c) (c).begin(), (c).end()
const int INF = 1<<29;

typedef double Weight;
struct Edge {
  int src, dst;
  Weight weight;
  Edge(int src, int dst, Weight weight) :
    src(src), dst(dst), weight(weight) { }
};

bool operator < (const Edge &e, const Edge &f) {
  return e.weight != f.weight ? e.weight > f.weight : // !!INVERSE!!
    e.src != f.src ? e.src < f.src : e.dst < f.dst;
}

typedef vector<Edge> Edges;
typedef vector<Edges> Graph;

// // ¹öª¢çÈ¢ê
vector<Weight> dijkstra2(const Graph &g, int s) {
  vector<Weight> dist(g.size(), INF);
  dist[s] = 0;
  priority_queue<Edge> Q; // "e < f" <=> "e.weight > f.weight"
  for (Q.push(Edge(-2, s, 0)); !Q.empty(); ) {
    Edge e = Q.top(); Q.pop();
    if (dist[e.dst] < e.weight) continue;
    FOR(f,g[e.dst]) {
      if (dist[f->dst] > e.weight+f->weight) {
        dist[f->dst] = e.weight+f->weight;
        Q.push(Edge(f->src, f->dst, e.weight+f->weight));
      }
    }
  }
  return dist;
}

int main() {
  int n;
  while(cin>>n,n) {
    int a[n+1];
    a[0] = 0;
    REP(i, n)
      cin >> a[i+1];
    double b,r,v,e,f;
    cin>>b>>r>>v>>e>>f;
    double timetable[10001];
    timetable[0] = 0;
    REP(x, 10001) {
      double t;
      if (x >= r) t = 1.0/(v-e*(x-r));
      else t = 1.0/(v-f*(r-x));
      timetable[x+1] = timetable[x] + t;
    }
    
    Graph g(n+1);
    REP(i, n) {
      for (int j=i+1; j<n+1; ++j) {
        double t = 0;
        if (i) t += b;
        t += timetable[a[j]-a[i]];
        g[i].push_back(Edge(i,j,t));
      }
    }
    printf("%.12f\n", dijkstra2(g, 0)[n]);
  }
}