This is the last of the set of real analysis questions. Any help would be greatly appreciated:

A series is said to be Abel-summable to L if the power series

f(x) = a_n*x^n converges for all x Є [0,1) and L = lim f(x) as x approaches 1 from the negative side.

a. Show that any series that converges to a limit L is also Abel-summable to L.

b. Show that (-1)^n is Abel-summable and find the sum.