Help please

I am having troubles in doing this rational rose task, and was wondering if ther was anybody that could give me a possible guideline!!!!!

Question:
A retail outlet sells various items through its catalogue sales. A customer chooses a list of items, which he/she wishes to purchase. Each item is listed together with a description and its weight, which influences the cost of transporting the order. For each item, there will be a reduction in price for purchasing in quantity. A customer order will be dated and will have a status value, which indicates whether the order is paid, due for payment or overdue for payment. For each order the total, the VAT and the total weight of the order will be calculated separately. These are calculated by adding together the sub-totals and weights which have been calculated for each item in the order. The company maintains a database of customers, with details such as name and address. A customer can have more than one order pending. Payment can be made in 1 of 3 ways, by credit card, cash or by cheque. For a credit card transaction, the number, type of card and its expiry date must be known. Credit cards and cheques must be authorised before a transaction can take place. For a cheque, the account name plus the bank sort code must be known before the cheque is authorised.