we know that
Based on the table
Percent%=[1-Decay factor]*100%
so
for decay factor=0.98
Percent%=[1-0.98]*100%----> 2%
for decay factor=0.50
Percent%=[1-0.50]*100%---->50 %
for decay factor=0.64
Percent%=[1-0.64]*100%----> 36%
for decay factor=0.23
Percent%=[1-0.23]*100%----> 77%
therefore
the answer is
36%
