The 80/20 rule is a concept that suggests:a) 80% of inventory should be readily available, and 20% should be reserved for emergency demand b) 80% of a firm's first time users will become brand loyal an 20% of the first time users will use the product only once c) 80% of a firm's sales are obtained from 20% of its customers d) 80% of a firm's expenditures are tax deductible and 20% are not