A week after a Boxing Day sale, a sample of customers were asked by a researcher to describe how they now feel about their Boxing Day purchases $-$ Satisfied, Neutral, or Dissatisfied. The responses are presented in the pictograph below, where each icon represents the same amount of people:

How do you feel about your purchase?

a$.$ What percent of the shoppers felt neutral about their purchase?

$\%$

b$.$ If $480$ shoppers were sampled, how many of them were dissatisfied with their purchase?

shoppers

c$.$ If $117$ of those sampled felt dissatisfied, how many were sampled in total?

shoppers

d$.$ If $135$ of those sampled felt dissatisfied, how many felt neutral? shoppers