string concatenation

In the sheet, i already had a few columns:

string1string2 string3
001 1 1.5
001 2 6.4


I'd like to add a new column and concatenate the strings in previous columns with additional characters:

string1 string2 string3 string4
001 1 1.5 c-001-b01_1_5x
001 2 6.4 c-001-b02_6_4x
002 3 7 c-002-b03_7x

Is there a good way to do this? Thanks in advance.