I need 3 scripts to communicate with a Lightspeed webshop using API -- 2

I have a client with a Lightspeed webshop. I have API keys to connect to the shop. I need 3 scripts for this project in PHP.
All products have an ArticleCode. The client wants to adjust the stock of the products with a php page, using a barcode scanner. The scanner will read the ArticleCode number from the product and submit that to the PHP script page that is connected with the API to Lightspeed.

I need:
1. a PHP script that does a lookup with the ArticleCode to retrieve / display the
* product image
* the product name
* the variant size
* the product price
* the stock of the variant

2. I need a PHP script that will the stock amount of a variant, using the ArticleCode (with any given number, +1, +2, +3 etc)

3. I need a script that does the same as point 2, but then multiple products at the same time.

This is the info from Lightspeed:
https://developers.lightspeedhq.com/ecom/endpoints/variant/#get-retrieve-a-variant

Please answer the following:
-How long will it take you to deliver the work
-How much do you charge for all 3 scripts?