Available cash when transferring from SPAXX to FDLXX

Let's say I have a grand total of $100 in SPAXX in my account.

• Monday at 10 AM I sell all $100 of my SPAXX to buy $100 of FDLXX.
• Monday at 12 PM I attempt to make a $50 purchase with my Fidelity debit card.

Since money market transfers happen after hours, what exactly would happen?

• Would my debit card transaction get declined?
• Would my SPAXX to FDLXX order still go through, but would only receive $50 as FDLXX?
• Would the whole SPAXX to FDLXX transaction get cancelled?

Thanks!