"button_to" for custom action not working.

[Padmahas Bn]

First thing is I'm no using form_for or any other form tags.

I have a Model

class Modelname < ActiveRecord::Base
  def self.methodfirst       #Class method
   :
   # Some code
   :
  end
 
  def methodsecond           #Instance method
   :
   # Some code    
   :
  end
end

a controller

class SomenamesController < ApplicationController
   
 def new
    @variable = Modelname.new
  end
 
  def create    
    Modelname.methodfirst            # calling class method methodfirst 

    redirect_to(new_somename_path)
  end
 
  def deduction
    Modelname.new.methodsecond       # calling instance method methodsecond
  end
   
end

a partial file  _form.html.erb rendered from new.html.erb

<div class="row">
 <div class="actions">
      <%= button_to "create action", somenames_path, :class => "btn btn-primary" %>
    </div>
   
    <div class="actions">
      <%= button_to "deduction", action: "deduction", :class => "btn btn-primary", method: "post" %>
    </div>
</div>

new.html.erb

<%= render 'form' %>

Problem is: First button is working fine but not the second

<%= button_to "Start recovery printing", recoveries_path, :class => "btn btn-primary" %>

is working fine. Since it calls "create" action inside Somenames

But the second button is not working but throwing an error message

No route matches {:action=>"deduction", :class=>"btn btn-primary", :controller=>"recoveries", :method=>"post"}

Now how can I call custom action "deduction" written inside Somenames controller so that it will call instance method "methodsecond"