21. The total price of six cans of coke is $21.
(a) Find the price of coke in $/can.
(b) A 10% discount will be offered on the purchase of 12 cans of coke.
(i) Find the total price of 12 cans of coke.
(ii) Find the price of coke in $/can if May buys 12 cans of coke,