Answer:
0.064
Step-by-step explanation:
Number of days in a year = 365
Mean rate of false alarm in a year = λ = 365 * 0.2 = 73
Standard deviation, σ = sqrt(λ) = sqrt(73) = 8.54 (for large λ value)
Using the relation :
P(x < 60): (60 - 73) / 8.54
P(x < 60) = - 1.52
P(Z < - 1.52) = 0.06426 (Z probability calculator
= 0.064
