There are 90 people in the restaurant. The probability of someone ordering a drink with the food is 60%. Use Normal approximation of Binomial...

There are 90 people in the restaurant. The probability of someone ordering a drink with the food is 60%. Use Normal approximation of Binomial Distribution to answer the following 6 questions.

5. What is the probability that less than 50 people will order a drink?

6. What is the probability that between 52 or more and 56 or less people will order a drink? 

 I got the wrong answer. I used Mu=np=54.Then sdev=Sqrt(54(1-.6)=4.6475

Then 50-54/4.6475=-.86067

Can you help me understand how I got the wrong answer?