How much should I charge for commissions?

Hi, I like doing digital character art and 2d animation and I want to start online comms. These three took around 9-15 hours each. How much would you pay for something like this? I was thinking I could price it by a base Character Art price + Extra X% per character + Extra for background. Maybe I could also offer sketches but idk how I’d price that. I’d appreciate any advice on ways to go about it. Not sure what would be best to get customers and a decent income cus I know it’s competitive out there!