Taxable benefits John

Hi, I have a question on "Employment income". In BPP this is question 47 - John is employed y Zebra Plc and gets a laptop. Provided computer personal use: 6 November 2018 Market value first provided 3500 GBP Market value when provided to John 2000 GBP Zebra gave the computer to John on 5 April 2020 with a market value of 1000 GBP. WHat is the total taxable benefits? The answer says 3300 GBP, or 2990 GBP if the first year of provision was taxed in full , 1720 GBP using the lower value for the gift and 1833 GBP is using the 2000 when the asset was provided. I'm a bit confused on how did they get to these answers, any help is appreciated.