Every contract to which a public body of this
state is a party, requiring the employment of skilled mechanics,
skilled workmen, semiskilled mechanics, semiskilled workmen
or unskilled labor in the performance of public work, must contain
in express terms the hourly and daily rate of wages to be paid
each of the classes of mechanics and workmen. The hourly and
daily rate of wages must be posted on the site of the public
work in a place generally visible to the workmen.