纸浆找不到解决方案

Question

我正在尝试使用 Python 中的 Pulp 模块找到问题的最佳解决方案。我的问题出在照片上。我在 Pulp 中写了这个问题，但我发现这个问题是不可行的（状态 -1）。我知道这个问题有解决方案，但我必须在代码中犯一些错误（当我改变变量是连续的问题有连续的解决方案时）。 感谢您的帮助。

import numpy as np
# Import PuLP modeler functions
from pulp import *

# Creates the 'prob' variable to contain the problem data
prob = LpProblem("Computer company service problem", LpMinimize )
demand = {1: 6000, 2: 7000, 3: 8000, 4: 9500, 5: 11500}

# A dictionary called 'Vars' is created to contain the referenced variables(the routes)
vars_x = LpVariable.dicts("x", range(1,6), 0, None, LpInteger)
vars_y = LpVariable.dicts("y", range(1,6), 0, None, LpInteger)

# The objective function is added to 'prob' first
prob += lpSum([15000*vars_y[i] + 7500*vars_x[i]  for i in range(1,6)]), "Sum_of_employee_cost"

# The demand minimum constraints are added to prob for each demand
for i in range(1,6):
    prob += 160*vars_y[i]-50*vars_x[i]>=demand[i], f"Reach demand in month {i}"
    
# The demand minimum constraints are added to prob for each demand node (bar)
prob += vars_y[1]==50, f"Workers in month {1}" 


for i in range(2,6):
    prob += 0.95*vars_y[i-1]+vars_x[i-1]==vars_y[i], f"Workers in month {i}" 


prob.solve()