The mean cost of an airline ticket from Los Angeles to Hawaii is $638 with a standard deviation of $138. The cost distribution is known to be bell-shaped. Use this information in all remaining problems on this exam. Question 18 3 pts Estimate the percentage of tickets cost at least $471. 0 68% o 84% o 16% O 81.5% Question 19 3 pts Would it be unusual for a ticket to cost $990? Why or why not? Explain and support your response in a full sentence