The front girl, Mary, is a student in a lab.  She is doing an experiment, perhaps research for her professor.  She is careful to make proper measurements; she wants her professor to be happy, and she appreciates the importance of accurate results.  Though she is not intensely focused, she honestly thinks of nothing else while she studies the quantities and compositions of the substances she works with.  It is not that she is driven for chemistry in particular, but she does not have a lot on her mind.  She knows what she has to do, and she does it.  The woman in the back observes Mary.  She has done these routine type experiments hundreds of times before, and she gets a kick out of watching the new generation participate in the scientific way of doing things.
