How to do b? I found out that p=0.84 q=0.16 n=90 and Std Dev=sqrt(0.84*0.16)/sqrt(90)=0.0386 and then I used the z formula 0.04/0.0386 to get the z value 1.035 and using the table converts into 0.85 and it was wrong. I want to know which step I did wrong.

A company makes auto batteries. They claim that 84% of their LL70 batteries are good for 70 months or longer. Assume that this claim is true. Let E! be the proportion in a random sample of 90 such batteries that are good for 70 months or more. a. what Is the probability that this sample proportion is within 0.03 of the population proportion? Round your answer to two decimal places. P: c.5545 b. What is the probability that this sample proportion is less than the population proportion by 0.04 or more? Round your answer to two decimal places. P