Ruby on Rails

Hello,

Below are my Models and Tables/Migrations and I want Query Code based on them

Model: FinanceFeeCategory
Table: finance_fee_categories
Fields:  id,name,batch_id

Model: FinanceFeeParticular
Table: finance_fee_particulars
Fields: id,finance_fee_category_id,student_category_id,admission_no,batch_id, due_date

Model: Batch
Table: batches
Fields:  id, name




Relationships:

class FinanceFeeCategory < ActiveRecord::Base
  belongs_to :batch
  belongs_to :student
  #
  has_many   :fee_particulars, :class_name => "FinanceFeeParticular"
  has_many   :fee_discounts
  has_many   :batches,:through=>:category_batches
  has_many   :category_batches
 
 class FinanceFeeParticular < ActiveRecord::Base
  belongs_to :finance_fee_category
  belongs_to :student_category
  belongs_to :receiver,:polymorphic=>true
  belongs_to :batch
  has_many   :fee_discounts
 
 
  class Batch < ActiveRecord::Base

  belongs_to :course

  has_many :students
  has_many :fee_category , :class_name => "FinanceFeeCategory"
 
 
  I am Using Rails 2.3.5 and Ruby 1.8.7
 
  Now I have a Dropdown filled with batches I want to populate another Dropdown with Fee Categories based on the
  Batch selected

And then a 3rd dropdown with Particulars based on the Category selected

and the need a Query to get all the Students admission_no
  based the Due_date if less the Currenct Date for Each the Particular I select from drop down.
 
  Pls someone help me in this.

Thanks in advance.