A

store

owner

increases

the

price

of

a

n

$

8

0

pair

of

shoes

by

2

0

%.

After

a

few

weeks,

because

of

falling

sales,

the

owner

reduces

the

price

of

the

shoes

by

20%.

A

customer

notices

the

change

and

says

they

are

back

to

the

original

price