last Monday前用什么介词，Sunday morning呢

英语中 last monday 到底是哪一个星期一?
假如今天是星期四,那么 last monday 到底是哪一个星期一?
这一周的星期一还是上一周的星期一?
是不是要看说的环境了？

英语翻译
Dear Chen Jie
,
How is it going?Last Monday
,
we talked
about
our dreams
in
the
class
meeting
．
Some
students didn’t know what they wanted to be in
the
future
．
But
I
said
that
I
wanted
to
be
an
English teacher
．
I hope to be a good teacher
,
like
Mr.
Wu
．
He
makes
his
math
class
interesting
．
He often tells us to work hard and
try our best to achieve our dreams
．
What are you going to be when you grow
up?
Yours
,
Li Ming
Li Ming
Dear Li Ming,
Thanks for your letter.My dream is to be a
voluntary(
志
愿
者
)
doctor.
But
my
parents
don
’
t
agree
with
me.
They
think
the
job
will
sometimes be very different.This week,I wrote
to
my
Chinese
teacher,
Miss
Liu.
I
asked
her
for
some
advice.
She
said
that
a
good
doctor
could help more people and she told me not to
give up my dream.Now,I
’
m sure of my dream
job and maybe I will go to work in a poor place
one day,but I will always be your friend!
Love
Chen Jie