Find average of numbers appearing in same cell

[caabdul]

Hi Gurus

Please find file attached.

I have cells where there appear years more than once, like follows

CeLL A2 = "a - 2013 xyz - 2014 n - 2016"
CeLL A3 = "some 2013 as well as 2016"
CeLL A4 = "2015, and 2018"

Is it possible to get following results
B2 = Average of years in Cell A2
B3 = Average of years in Cell A3
B4 = Average of years in Cell A4

Regards