Find all values of x where the function f(x) = 7x² + 8x - 4 is discontinuous. For each value of x, provide the limit of the function as x approaches a. Note when the limit doesn't exist.
a) x = -8, Limit = 20
b) x = 0, Limit does not exist
c) x = 1, Limit = 11
d) x = 2, Limit = 32