A Laptop Battery Lifespan Follows a Normal Distribution with Mean $\sigma$

Multiple Choice

A laptop battery lifespan follows a normal distribution with mean μ = 20 months and a standard deviation $\sigma$ = 6 months.To test the alternative hypothesis that μ > 20 with α = .05, 36 laptop batteries are randomly selected.Assuming that μ = 21, the power of this is approximately ________.

A) 0.00
B) 0.2595
C) 0.2036
D) 0.6449
E) 0.7405