The project optimistic estimate is 10 weeks and the pessimistic estimate is 40 weeks. What is the standard deviation of the estimate?

Thanks for invitation ..No. b- 5...........................SD = (p − o)/6

Answer is 

B:  5

40-10/6 OR 30/6 = 5

thanks for invition ,,,,,,,,,, my choice is option B

Agree on expert answers. Thanks

B – By straight calculation: (40-10)/6 or 30/6 = 5