What you need to know on Wall Street today

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The Federal Reserve is expected to raise its benchmark interest rate again on Wednesday. Here's what you need to know:

• Only one thing matters at Wednesday's Fed meeting
• Janet Yellen's farewell at the Fed has become more complicated
• The Fed is about to raise interest rates again - here's how it happens and why it matters
• The shrinking role of unions helps shed light on an economic trend that is puzzling Fed officials
• Check back here for the latest news and analysis on the Fed's decision

Elsewhere in D.C. news, Republicans have a final deal on their tax bill - here's what's in it. And there's one more reason for Republicans to be very nervous about the Senate in 2018, according to Josh Barro.

Back on Wall Street, a top exec at trading giant Virtu is out. The mysterious trader known as "50 Cent" has lost $197 million betting on a stock market meltdown. Robinhood is launching a free options trading product for its users.

And here's what it takes to launch a hedge fund right now, according to the Wall Street pros who know

In markets news, the ghosts of the financial crisis are costing investors a fortune. A wildly popular stock market strategy is hotter than ever.

In deal news, Target has a new $550 million weapon to defeat Walmart and Amazon, and Saudi Aramco has reportedly asked banks to pitch for a role in its IPO.

And in tech news:

• Apple's Shazam deal is a sneak attack to hit Spotify where it hurts
• Finisar soars after Apple announces $390 million investment
• RBC: Nvidia can't profit from bitcoin anymore - but the boost from cryptocurrencies is just getting started
• T-Mobile is becoming a cable TV provider
• GOLDMAN SACHS: 4 big tech companies will own 65% of the cloud market
• A Hungarian startup thinks it has the key to cheaper self-driving cars - but a ride in its test car suggests it has a lot of work ahead
• As bitcoin skyrockets, a top Facebook exec is joining the board of Coinbase, the cryptocurrency exchange
• A board member has resigned at Tezos, the tumultuous cryptocurrency startup that raised $232 million

Lastly, we drove a $73,000 Cadillac XTS V-Sport and completely fell for its retro charm and secret power.