Personal bank account management procedures [simplified]

//Self-study, I can't understand T_T for the sentence "get the daily accumulated value of the deposit amount up to the specified date". Therefore, modify part of the content of the class and ignore part of the logic =_=…

#include <iostream>   
#include <cmath>  
using namespace std;

class SavingsAccount { //Savings account class
private:
	int id; //account
	double balance; //balance
	double rate; //The annual interest rate of the deposit
	double interest=0.0; //interest   

	//Record an account, date is the date, amout is the amount, and desc is the description
	void record(int date, double amout);

public:
	SavingsAccount(int date, int id, double rate);
	int getID() { return id; }
	double getBalance() { return balance; }
	double getRate() { return rate; }
	void deposit(int date, double amount);
	void withdraw(int dadte, double amount);
	

	//settlement interest
	double lixi(int date, double amount);

	//display account information
	void show();
};


// Implementation of SavingsAccount related member functions
SavingsAccount::SavingsAccount(int date, int id, double rate)
	:id(id), balance(0), rate(rate) {
	cout << date << "\t#" << id << " is created" << endl;
}

void SavingsAccount::record(int date, double amount) {
	amount = floor(amount * 100+0.5)/100; //The purpose of the floor function: keep two decimal places
	balance += amount;
	cout << date << "\t#" << id << "\t" << amount <<"\t"<< balance << endl;
}

void SavingsAccount::deposit(int date, double amount) {
	record(date, amount);
	lixi(date, amount);
}

void SavingsAccount::withdraw(int date, double amount) {
	if (amount > getBalance()) //If the money to be withdrawn is greater than the deposit balance
		cout << "Error:not enough money" << endl;
	else
		record(date, -amount);
	    lixi(date, -amount);
}
 

void SavingsAccount::show() {
	cout << "#" << id << "\tBalance:" << (balance+interest)<<endl;
	cout << "#" << id << "\tlixi:" << interest;
}


double SavingsAccount::lixi(int date, double amount) { //Calculate deposit interest under different operations and accumulate
	interest += ((amount*rate) / 365)*(90 - date);
	interest = floor(interest * 100 + 0.5) / 100;
	return interest;
}

intmain()
{
	//create two accounts
	SavingsAccount sa0(1, 21325302, 0.015);
	SavingsAccount sa1(1, 58320212, 0.015);

	//several accounts (operations)
	sa0.deposit(5, 5000);
	sa1.deposit(25, 10000);
	sa0.deposit(45, 5500);
	sa1.withdraw(60, 4000);

	// output each account information
	sa0.show();  cout << endl;
	sa1.show();  cout << endl;

	return 0;
}