In a bakery, there were a total of 900 cakes and cookies.

70% of them were cakes. After some of the items were sold, the number of cakes decreased by 20%.

In the end, 10% of the items in the bakery are cookies.

(a) How many cookies were sold in all?

(b) If the selling price of a cookie is $1.50 a piece, how much was collected from the sale of the cookies?

Notes to students:

1. If the question above has parts, (e.g. (a) and (b)), given that the answer for part (a) is 10 and the answer for part (b) is 12, give your answer as:10,12