Percentages involving Finances: Discount

A book at bookstore A is marked at \(\$30\) but sold at \(\$24\). Another bookstore B sells this kind of book at \(\$28\) after a percentage discount of \(30\%\). And bookstore B offers a further percentage discount of \(20\%\) on each book after the first 100 when more than 100 books are purchased.

1. Find the percentage discounts of the book at bookstore A.
2. Find the marked price of the book at bookstore B.
3. Find the selling price and the overall percentage discount of the book at bookstore B for the part of purchasing beyond \(100\).
4. A school is planning to buy this kind of book for the students. Find which bookstore, A or B, has a cheaper total price if the school wants to buy \(400\) such books.
5. Find the minimum number of books one will find it cheaper to buy from bookstore B than bookstore A.