Solo 401k Contribution

Hello-

Husband owns a business. Wife is part-time W2 of the business. No other employees. It is an LLC that flows to Schedule C. A Solo 401k was set up through a third party March 2025. No contributions have been made yet. A tax return extension was filed.

Wife’s W2 is $10K through the business. Business net on Schedule C is $20K.

What contributions can be done for 2024?
Husband Employer: $20,000 * 20% = $4,000?

Wife Employer: $10,000 * 25% = $2,500?

Husband After-Tax: $20,000?

I am certain some of the contributions are off above. Any insight would be appreciated!