Mention the Control chart that is suitable for the following scenarios:

a$.$ The operators of automated sorting machines in a post office must read the ZIP code on a letter and divert the letter to the proper carrier route. Over one month's time, $25$ samples of $100$ letters were chosen, and the number of errors was recorded.

b$.$ A quality engineer at an automotive parts plant monitors the lengths of camshafts. Three machines manufacture camshafts for three shifts each day. The engineer measures five camshafts from each machine during each shift.

c$.$ A quality engineer wants to evaluate the stability of a line that produces leather jackets. Once in each hour a jacket is selected atrrandom from those made during that hour. Small imperfections $($missed stitches; zipper catch; button missing; and loose threads$)$ are counted.