def pop_bottle_recycler(investment)
  # Calculates no. of bottles bought
  amount = bottles_bought(investment)

  unless condition
    total_bottles = 0
    total_bottles = amount + amount/2 + amount/4
    remainder_caps =
  end

end

# Returns how many bottles the customer can get for his investment
def bottles_bought(investment)
  investment.to_i/2
end

# Returns how many free bottles the customer gets for recycling a certain number (num) of empty bottles
def empty_bottles_reward(num)
  num/2
end

# Returns how many free bottles the customer gets for recycling a certain number (num) of bottle caps
def bottle_caps_reward(num)
  num/4
end

# Return total reward a customer can get with a certain amount of bottles
def total_reward(num)

end

puts pop_bottle_recycler(20)