The graph below shows the amount of money charged by two electricity providers per month, depending on the amount of electricity used. a) Catherine uses 240 kWh of electricity per month. Which provider would be cheaper for Catherine? b) Stephanie uses 140 kWh of electricity per month. How many more kWh of electricity would Stephanie have to use per month to mean that she would be charged the same amount of money by provider A as by provider B? If your answer is a decimal, give it to 1 d.p. y Cost per month (£) 0 Provider A y = 72 +15 Provider B y = 26 +25 Electricity usage per month (kWh)