Translation:The coat is small, therefore I am buying a new coat.
It's interesting that in Arabic, L-K-N has the opposite meaning— "although", rather than "therefore". (y)
But لكن is not related to לכן. The word לכן is actually made up of ל + כן: "for" + "such", so it doesn't come from the root L-K-N. And as you will hear, the pronunciation is lakhen, with a sound like خ.
This has come up more than once as a listening exercise, but doesn't seem to have any audio track to listen to! Is anyone else having the same problem?