business law - contract

各位讀過 business law的朋友，可否幫幫忙解答以下問題：

Which, if any, of the following are offers capable of acceptance?
(a)a department store leaflet offering pool furniture at a 50% discount
(b)as for (a) above, but also offering “rainchecks” for those unable to be supplied from current stock
(c)a display in a store window of a video recorder with a $500 price tag

：)謝謝各位幫忙