The answer to this problem is $$0.$ Please explain why.

Keller Korp. signed a contract with a customer on July $1,2020$ to sell them $100$ units of inventory for $$10,000.$ Keller prepares financial statements for a December $31,2020$ year$-$end. The following events occurred:

The customer pays Keller Korp. the $$10,000$ on August $1,2020.$

Keller Korp. delivered $25$ units on September $1,2020$ and plans to deliver the remaining $75$ units the following year.

What is the value of the liability that Keller Korp. records on July $1,2020?$