Answer:
A. 0.4082
Step-by-step explanation:
According to the given data
mean 'μ' =50
standard deviation 'σ'=15
In order to find the probability for 50<x<70
, we use the standard form
Z= (x−μ)
/σ
when x=50, Z will be zero
therefore, Z=0
when x=70,
Z=(70−50)/15
Z= 20/15
Z=1.33
next is to find the probability for 50<x<70
for standard form 0<z<1.33
By using Z-table, the area is equal to 0.4082
Thus, probability that the length of time will be between 50 and 70 hours is 4082
