What is the Rand Formula? $($pp$.487-88)$

a$.$ Named for Justice Ivan Rand, the Rand Formula mandates that all workers in a given workplace must join a union if $50$ percent of the workers have voted to do so

b$.$ Named for Justice Ivan Rand, the Rand Formula refers to the requirement that dues will automatically be checked off and are payable by all bargaining unit members whether or not they choose to join the union

c$.$ Named for the senator who sponsored it$,$ the Rand Formula bestows union recognition rights on workers who can demonstrate that a majority of the workplace seeks to unionize

d$.$ The Rand Formula is a mathematical formula used to calculate the amount of dues unionized workers must pay to their union based on the income that the union has negotiated on their behalf