I’m almost done solving this
Answer: The size of sample of 193 is needed.
Step-by-step explanation:
Since we have given that
Margin of error = 6%
At 90% confidence level, z = 1.645
Let p = 0.5
and q = 0.5
( because it is the most conservative estimation).
So, using formula, we get :

Hence, the size of sample of 193 is needed.
He mails
(1000) x (the number of weeks he keeps it up)
of them.