（1）编写一个程序，创建5 个Loan 对象，将它们写入一个名为Exercise12_6.dat 的文 件中。

（2）假定已经创建了一个名为Exercise12_6.dat 的文件。

编写一个程序，从文件中读取 Loan 对象，并计算总贷款额。假定你不知道文件中保存了多少个 Loan 对象。使用eof（） 来检测文件末尾。-(1) Write a program to create five Loan objects, they are written in a file named Exercise12_6.dat.

(2) assuming that you have created a file named Exercise12_6.dat s.

Write a program that reads the Loan object from a file, and calculate the total loan amount. Suppose you do not know how many Loan object file saved. Use eof () to detect the end of the file.