A=14 units and B=7 units.
As in SRTF the new process is scheduled when its Remaining time is minimum.
B.T. of A= 6 + value greater than 2 + value greater than 4 (as B replaced it so its remaining time is lesser A than remaining time of B and after that C replaces B which means remaining time of B is greater than remaining time of C )
B.T. of A =6+3+5=14
B.T. of B=2+5=7