Just remove the comma like this:
From the standard
7.5.2 Element identifiers: the id and class attributes
Attribute definitions
id = name [CS]
This attribute assigns a name to an element. This name
must be unique in a document.
class = cdata-list [CS]
This attribute
assigns a class name or set of class names to an element. Any number
of elements may be assigned the same class name or names. Multiple
class names must be separated by white space characters.
Yes, just put a space between them.
Of course, there are many things you can do with CSS inheritance. Here is an article for further reading.