Stuff

loan.rb

class Loan
  def initialize(amount, term_in_months, rate)
    @principle = amount
    @term = term_in_months
    @rate = rate

    # Calcluate Initial Interest
    @interest = some_formula
  end

  def pay_amount(amount)
    # meh
  end

  def pay_principle(amount)
    # Do crap here
  end

  def pay_interest(amount)
   # Do other crap here
  end

  def should_i_invest
    # code
  end
end