3 blarsfs and 18 crobs in a minute

so

6 blarsfs and 36 crobs in 2 minutes

that is

6 blarsfs and 34 crobs +2crobs in 2 minutes

but we are told that there are

7 blarsfs and 2 crobs in two minutes

so

There must be 34 crobs in 1 blarsfs

and

3*34+18 = 120 crobs in a minute

so one crob is a half second

9 blarfs and 6 crobs = 9*34+6 = 312 crobs = 156 seconds