Around $6.9M for Beauty and the Beast on Monday, down ~49% from last Monday.
If the rest of the week is similar, we are looking at a little shy of $350M going into next weekend. That means BatB could possibly crack the $400M domestic mark in 17 days. Age of Ultron took 24 days.
Here are the second Mondays for the other March-May films with opening weekends within 10% or so of BatB's $175M.
Age of Ultron - $5.4M
Civil War - $4.75M
Iron Man 3 - $4.6M
The Hunger Games - $4.5M
Batman v Superman - $3.2M
The Jungle Book made $4.2M on its second Monday.
None of the films between Age of Ultron ($460M) and The Dark Knight ($535M) opened in the spring for a meaningful comparison. The Avengers made $7.9M on its second Monday, but I think it is clear that BatB isn't going to crack $600M.