How much is the missing bike fee for Citi Bike?

Excuse me, could you please clarify for me what the exact amount is for the missing bike fee imposed by Citi Bike? I'm curious to know if there's a standard charge that's levied whenever a rented bike goes unaccounted for, or if the fee varies depending on certain circumstances. Understanding this information would be very helpful for me as a potential user of their service. Thank you for your assistance.