For
online
retailers
,
Black
Friday
____________________
a
particular
challenge
.
Demand
in
the
UK
last
year
____________________
30%
higher
than
predicted
.
Tesco
stores
could
no
longer
____________________
next
-
day
delivery
.
Other
stores
had
the
same
problem
,
and
____________________
certain
orders
up
to
two
weeks
late
.