For RR
$_{0}A_{1}B_{2}A_{3}B_{4}A_{6}//_{7}A_{8}B_{9}A_{10}B_{11}A_{13}$
at t=4 B goes for I/O which will be completed at t=8
at t=6 A goes for I/O which will be completed at t=7
at t=11 B goes for I/O which will be complete at t=15
at t=13 A goes form I/O which will be complete at t=14
TAT of A = Completion - Arrival = 14-0=14
TAT of B = Completion - Arrival = 15-0=15
SRTF
$_{0}A_{1}B_{3}A_{6}//_{7}A_{8}B_{10}A_{13}$
at t=10 B goes for I/O complete at 14
at t=13 A goes for I/O complete at 14
TAT A=B=14
or
$_{0}A_{1}B_{3}A_{6}//_{7}B_{9}A_{13}$
at t=9 B goes for I/O complete at 13
at t=13 A goes for I/O complete at 14
TAT A=14 B=13