we have I1->I2-> I3->I7-> I8->I9 total instrustions to execute.
n= no of instruction=6
no of stages =k=5
delay=max cycle time=tp=11+1=12 ns
branch panalty =4-1=3 cycle
total time to execute = time w/o stall +branch panalty overhead
=(k+n-1)*tp+ 3*tp
= (5+6-1)*tp+3*tp
=13 * tp =13*12=156 ns