How to add total price and date to subject line of staff order notification triggered by flow?

I created a flow that triggers a staff notification email whenever someone makes a purchase. In the subject line of that email I want to have the name, email, total price, and purchase date. 

This is what I have: {{ first_name }} {{ email }} {{ total_price }} {{ date }}.

Currently, however, only name and email appear when a notification is triggered. Total price and date do not appear. How can I get these to populate correctly?

My store is on Shopify. 

Thank you!