办妥了按揭贷款，请了律师，陈先生今天终于正式签订了买房合约。下面是他签约的过程：

S--Solicitor Mr. White 律师怀特先生

B--Client 1 Mr. Chen 客户一 陈先生

C--Client 2 Mrs. Chen 客户二 陈太太

S: Good morning. Mr. and Mrs. Chen. How are you?

早上好，陈先生，陈太太，你们好。

B: Fine, Mr. White. We are sorry for being late today. There was a traffic jam.

好，怀特律师，真对不起 ，我们迟到了，今天交通非常拥挤。

S: Don't worry. I have the contract ready for you to sign.

不用担心，我已准备好所有你们要签署的合约文件。

C: Thank you very much.

非常感谢。

S: Let me explain to you. Your property's address is Flat C, 5/F, Tong House Tai Koo Shing. The purchase price is four million and three hundred thousand dollars. You'll pay ten percent of the purchase price today, which is four hundred and thirty thousand dollars, and one cheque for stamp duty fee.

让我给你们解释一下。物业地址是太古城唐厦十五楼C室。成交价是港币四百三十万元。今天你们需要支付成交价的一成，即港币四十三万元，以及一张付印花税的支票。

B: How do you calculate¹ the stamp duty fee?

如何计算印花税？