$7.$ The resource$-$based view of competitive advantage states that for a firm to maintain sustainable competitive advantage it must control a set of exploitable resources that have four critical characteristics. What are these characteristics?

a$.$ inventory turns, high margins, long account payable periods, brand building relationships

b$.$ operational effectiveness, strategic positioning, scale, distribution channels

c$.$ rareness, value, imperfect imitability, non substitutability

d$.$ a website, an app, cloud$-$based systems, a savvy technology staff

e$.$ low margin, high delivery, infrastructure, customizable