The basic storage unit of a digital computer is a "bit". A bit is a storage position that can be disignated as either on $(1)$ or off $(0)$ at any given time. In converting picture images to a form that can be transmitted electronically. For example, a pixel with four gray levels can be coded using two bits by designating the gray levels by $00,01,10,11.$ How many gray levels can be quantized using a four bit code