interface User {
    id: number;
    name: string;
    email: string;
}
declare class UserManager {
    private users;
    constructor();
    addUser(user: User): void;
    getUserById(id: number): User | undefined;
    private loadUsers;
    updateUserEmail(userId: number, newEmail: string): boolean;
}
declare function calculateTotal(items: number[], taxRate?: number): number;
export { UserManager, calculateTotal };
