What is the product of the ratio of the current and the useful flux per pole?(a) product of ratio of current anduseful per pole = (useful flux per pole due to upper limit current * upper limit current) / (useful flux per pole due to lower limit current * lower limit current)(b) product of ratio of current anduseful per pole = (useful flux per pole due to upper limit current + upper limit current) / (useful flux per pole due to lower limit current + lower limit current)(c) product of ratio of current anduseful per pole = (useful flux per pole due to upper limit current – upper limit current) / (useful flux per pole due to lower limit current – lower limit current)(d) product of ratio of current anduseful per pole = (useful flux per pole due to upper limit current * lower limit current) / (useful flux per pole due to lower limit current * upper limit current)The question was posed to me in an online quiz.My question is taken from Motor Starters, Calculation of Resistance Steps & Design of Field Regulators topic in section Design of Small Electrical Machines, Starters and Field Regulators of Design of Electrical Machines