A conditional branch instruction evaluates the condition in the third stage of the pipeline.
So, branch penalty=2.
Assuming that 20% of all instruction executed are branch instructions.
Out of which 40% are conditional branches and 60% unconditional branches
50% of the conditional branch instructions the conditions are false
#stall cycle/instruction=$0.2*0.6*2+0.2*0.4*0.5*2=0.24+0.08=0.32$
Avg.inst exe. time=(1+# of stalls/inst)×cycletime$=(1+0.32)\times 1=1.32$