How can I add a checkout charge for reusable tote bags?

[salobm]

Hello everyone! 
The bags that I use for packing the products are reusable tote bags made up of natural fibers. 
I have 2 questions: 

1. I want to charge them at the checkout for orders below certain price. How do I customize this? 
2. is there an option like “would you like to add reusable tote bag for $10?” At the checkout? 
If anyone can help or have any idea on how to solve this it’s much appreciated! 

[MastersHub]

Do you have a Shopify Plus plan? If yes, you can proceed with both options. If not, you can choose option 2, but it will be applied to the cart. Are you a developer with a Shopify Plus plan? If yes, please follow the Checkout UI documentation. If not, consider hiring a developer.