Average data per row, based on column numbers

Hi everyone,

I have a huge amount of data, divided in 14 rows and 102328 columns. Now I want to average the data per row, but seperated for 5 groups of columns. Specificly I want the average from the data in row 1 to 14 for columns 1 to 11071. Same for columns 11072 to columns 15042 and so on.. Someone who can help me out?