c programming, thank you

a) What are the points of having different data types (eg char and int) that both store integer? Give a concrete example of a program or function where you can use char and int for calculations with integers. b) Most popular computers have bytes that are 8 bits in size, but there are also examples on computers with both larger and smaller bytes. A char in C always picks up a change. What is the largest and smallest value that can be stored in one unsigned char on a computer using bytes consisting of 4 bits instead of 8? Justify your answer with a calculation. c) What is the largest and smallest value that can be stored in a signed char (representing negative numbers with 2-complement) on a computer which uses bytes consisting of 4 bits instead of 8? Justify your answer with one calculation