A strain gauge is used to measure the strain on a vibrating beam which can vibrate up to a maximum frequency of 60 Hz. The strain gauge analog signal is converted in to a digital signal via an Analog to Digital Converter (ADC) in order to store the data on a computer hard drive. The engineer responsible for this measurement mistakenly selects a sampling frequency of 90 Hz for the ADC. (a) Determine the alias frequency due to the small sampling frequency. (b) Propose a sampling frequency that will not result into aliasing of the analog signal (make sure to provide your rationale for selecting this frequency).