What is a Quarter penny worth in Crispin:The Cross of Lead?

Actually there is a specific answer to this question in
the book.  It is in chapter 3 when the narrator who we later learn is Crispin is giving
us his history.  When at first, Crispin is telling us what a difficult life he and his
mother led, he tells that his mother's wages were.  Hers were a penny a day and she
could buy full loaves of bread on this.  So specifically. a quarter of a penny would be
worth a loaf of bread.