Beta Company is a property development company with A shares listed on the Shanghai Stock Exchange. On 15 June 2020, the Beta company signed an agreement with Omega company to lease an office building developed by itself to Omega Company. The start date of the lease was 21 July 2020. The office building was inventory before it was transferred to investment property on 21 July 2020. On 21 July 2020, the book balance of the office building was RMB450 million, and the fair value was 465 million. On December 31, 2020, the fair value of the office building was RMB495 million. In June 2021, the lease term expired, the company took back the office building and sold it for RMB 505 million, and the sales amount has been received. Beta measures its investment properties with a fair value model. Ignore any related taxes and fees. 

Required:

 (a) Prepare Journal entries for Beta Company the transactions on the relevant dates. 

(b) Beta owns an office building that comprises a portion that is leased out to earn rental income and another portion that is held for its own use as the headquarters of the company. Determine how Beta should classify this office building in its balance sheet and why?