Tesla CEO Elon Musk and Twitter are bracing for a legal fight after the  billionaire said Friday he was abandoning his $44 billion bid for the  social media company.

Twitter is vowing to challenge Musk in court to uphold the agreement.

Shares of Twitter slid more than 9% on Monday. Here's a look at what could happen next:

There are a lot of reasons why Musk might have had second thoughts.

But he alleged Friday that Twitter has failed to provide enough information about the number of fake accounts it has.

Twitter said last month that it was making available to Musk a  “firehose” of public raw data on hundreds of millions of daily tweets.

But Musk's lawyers have argued that the company was providing Musk with  sometimes “incomplete or unusable information” and less data than it  offers some of its big customers.

Twitter said last week it uses a mix of public and private data to determine the amount of spam.

Private user data isn't available publicly and thus isn't in the data “firehose” that it gave Musk.

That would include IP addresses, phone numbers and location.

Twitter said such private data helps avoid misidentifying real accounts as spam.

Twitter has said for years in regulatory filings that it believes about 5% of the accounts on the platform are fake.

But on Monday Musk continued to taunt the company, using Twitter, over what he has described as a lack of data.