su1_file 1
"abc"    6    8
"def"    7    9
"ghi"    2    5


su2_file 2
"abc"    60    8
"def"    70    900
"ghi"    20    5


su_file 3
"abc"    600    8
"def"    700    900
"ghi"    200    5


Output file:

Header    su_file1    su_file2    su_file3     average    ...mu1_    
mu2_    mu3_ etc....

abc    6    60    600    ***
def    7    70    700    ***
ghi    2    20    200    ***