In a certain year, Kwaku paid for electricity consumed each month as follows, the cost of the first 30 units was 10p per unit; the cost of the next 30 units was 7p per unit; the cost of each additional unit is 5p. (i) If Kwaku used 420 units of electricity in July that year, calculate the amount
he paid.
(ii) If Kwaku paid ¢27.10 in August last year, calculate the number of units of
electricity he used.
(iii) Find, correct to two decimal places, the percentage change in Kwaku‟s
consumption of electricity from July to August that year