Answer: a) 1267
b) 1509
Step-by-step explanation:
As per given , we have
Significance level : 
Using the z-value table , the critical z value for 98% confidence : 
Margin of error : E= 0.03
Formula for sample size :
, where p is the prior estimate of population proportion.
a) p=0.70
Sample size : 
Simplify , we get

Hence, the minimum sample size required = 1267
a) if no estimate of prior population proportion is given , we take p= 0.5
Sample size : 
Simplify , we get

Hence, the minimum sample size required = 1509