Question 1170821
Rule of 70 would exclude a and d.  70/6.15=11.38 favoring c
P=Po(1+(0.0615/12)^nt
2=(1.005125)^nt
ln2=nt ln 1.005125
nt=135.6 compounding times
divide by 12 to get years , which is 11.3
C