Two mechanics worked on a car. The first mechanic charged $55 per hour, and the second mechanic charged $70 per hour. The mechanics worked for a combined total of 25 hours, and together they charged a total of $1600 . How long did each mechanic work?

Thompson and thompson is a steel bolts manufacturing company. their current steel bolts have a mean diameter of 127 millimeters, and a variance of 36. if a random sample of 35 steel bolts is selected, what is the probability that the sample mean would differ from the population mean by greater than 0.5 millimeters? round your answer to four decimal places.