How to price a web app?

I just got my first ever private contract and I don't really know how to price it. While still needing to go over details and all, the general features are:

  1. Excel parsing - needs to be flexible as these documents come from their customers who don't use the exact format but is going to be very close. This is the main server action needed
  2. Excel file generation - generate with custom filters from the database populated from excel parsing.
  3. Tables, graphs, and charts visualizing the data on UI.

These are the app specific requests, while there can be more to be discussed still, I want to get a general idea of what I can charge. These are the main features needed. It will be an internal tool for a company with probably no more than 20 users using it.

Also the stereotypical features on an internal web app are expected such as:

Auth system (register only with company domain email),

Admin data management

User management

Error handling and alerting

Whole UI/UX development and design

etc..

How much or would I go about pricing this?