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

A series $\displaystyle \sum_{n=0}^{\infty}{{a_n}} $ is said to be Abel-summable to L if the power series

f(x) = $\displaystyle \sum_{n=0}^{\infty} $ 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 $\displaystyle \sum_{n=0}^{\infty} $ (-1)^n is Abel-summable and find the sum.