Final answer:
The expected number of weeks until the first failure occurs after a new array is installed is 20 weeks.
Step-by-step explanation:
To find the expected number of weeks until the first failure occurs after a new array is installed, you need to know the failure rate per week. Let's say the failure rate is 0.05 failures per week. The expected number of weeks until the first failure occurs can be calculated as the reciprocal of the failure rate, which is 1/0.05 = 20 weeks.