On 6 April 2021, an employer purchases a music system for £800 and immediately lends the system to an employee for his private use. The system remains in the employee's possession until 6 October 2023 when the employee buys it from his employer for £100, its market value on that day being £240. Calculate the taxable benefit in kind for tax years 2021- 22 to 2023-24 inclusive.