Find the domain and range of these functions

Find the domain and range of these functions. Note that in each case, to find the domain, determine the set of elements assigned values by the function.

a) the function that assigns to each nonnegative integer its last digit.
b) the function that assigns the next largest integer to a positive integer.
c) the function that assigns to a bit string the number of one bits in the string.
d) the function that assigns to a bit string the number of bits in the string.