The useful life of an electrical component is exponentially distributed with a mean of 1,000 hours. a. What is the probability the circuit will fail within the first 558 hours? b. Assuming 100,000 circuits have been made, approximately how many of these circuits will fail within the first 558 hours? a. The probability that the circuit will fail within the first 558 hours is 0.4276 . (Round to four decimal places as needed.) b. Number of expected failures within 558 usage hours = (Round to the nearest whole number as needed.)b. Calculate the mean and standard deviation of the cost of filling a job vacancy. The mean is 3297.84 . (Round to two decimal places as needed.) The standard deviation is 1199.64 . (Round to two decimal places as needed.) c. Assume the data are normally distributed. Determine the probability that the cost of filling a job vacancy would be between $2,000 and $3,000. The probability is. (Round to three decimal places as needed.)