Ultrasound is the name given to frequencies above the human range of hearing, which is about 20,000 hz. waves above this frequency can be used to penetrate the body and produce images by reflecting from surfaces. in a typical ultrasound scan, the waves travel with a speed of 1,809 m/s. for a good detailed image, the wavelength should be no more than 1.44 mm. what frequency is required?

Aproduction line at v. j. sugumaran's machine shop has three stations. the first station can process a unit in 7 minutes. the second station has two identical machines, each of which can process a unit in 16 minutes (each unit only needs to be processed on one of the two machines). the third station can process a unit in 10 minutes. ▼ is the bottleneck station, with a bottleneck time of nothing minutes per unit (enter your response as a whole number).