How much do my myself and my son need to show for 28 day to switch to Tier 4 dependent here in the UK. My wife is on a Tier 4 visa and her University is outside of London. Do I need to show - 1. £12240 (9 x 680 x 2) or 2. 21375 = £12240 + £9135 (£9135 is the maintenance that my wife showed initially...

I am presently on a Tier 4 Doctorate Extension Scheme Visa which expires on the 15th of June 2017. My wife and child are presently my dependant. My wife has begun her Master's studies this January 2017 on this visa but is travelling back to our country to make a Tier 4 visa application in April 2017...