SQL & PL/SQL

I have 10 different products in the product_detail table. Each of these products is a purchased one, so we have the customer information lying in different columns of the same table. Each product purchased is listed in the table. If a customer has purchased 4 different products, there are 4 rows for that customer and customer_Id is repeated 4 times. However each purchase is considered unique so a contract_ID is unique. So any time the combination od customer_Id and Contract_Id is unique throughout the table.

For example,
Customer_1 has 4 different contracts contract_1, contract_2, contract_3, contract_4). Contact_1 could be a desktop,Contact_1 could be a server,Contact_1 could be a Laptop, Contact_1 could be a desktop again. For each row this information is given column Item.

Question: How do I separate out the customers who have only one contract and the item is "LAPTOP".