Thaler has studied the impact of the default retirement plan option $("$opt$-$in$"$ or "opt$-$out"$)$ on the decision to enroll in a retirement saving plan. Changing this default option will affect the behavior of:

Question $5$ options:

a$)$

Humans only

b$)$

neither Econs or Humans

c$)$

both Econs and Humans

d$)$

Econs only