Sometimes key "B" doesn't work on my preinstalled keyboard even if "text to speech service is not enabled"

Although i have seen discussions on this topic before here and i tried all those options told by everyone,yet the problem persist with me.So here is the thing->-

Its been 3 weeks i bought new macbook pro and when i start using somtimes keys like "B" ,"G","-" stopped working eventually and after that i have to press long enough.Somtimes i pressed very hard and then after 4-5 seconds it started responding.But this is not a once behaviour.The occurance of this is 4/10.

The text to speech service and mouse keys options are diabled already.

please help.