Why is this method protected? (from agile book)

Hi, this would work because for the simply fact that :minimum isn't a
configuration option for validates_numericality_of. At this time, the
config options are as follows:

Configuration options:

message - A custom error message (default is: "is not a number")

on - Specifies when this validation is active (default is :save, other
options :create, :update)

only_integer - Specifies whether the value has to be an integer, e.g.
an integral value (default is false)

allow_nil - Skip validation if attribute is nil (default is false).
Notice that for fixnum and float columsn empty strings are converted
to nil

Good luck,