How can I get inside Muhlhaven's room?

Hint 1 of 5:

Going through the door normally without a key is not an option right now.

Hint 2 of 5:

While facing Mulhaven's door, look up.

Hint 3 of 5:

Another tool might pry the top of the door open.

Hint 4 of 5:

Look on the service cart.

Hint 5 of 5:

Find a knife.