chebychev's inequality

Hi all, I have a question that I can't find answer to: I have 10 random variables X1, X2....X10 which are all independent and exponentially distributed with parameter=2 Xi~exp(2) for i between 1 and 10. Now the argument says that the probability that the sum of all 10 X's is larger...

Xn are iid Exponential(.5). After using the central limit theorem, Xn is Normally distributed. Use chebychev's inequality to find out how large n be so that P(|Xn-2| < .01) > .95. I tried working on it and got the E(Xn) = 2n and Var(Xn) = 4n, and P(|Xn-2n| > .01) < (4n/(.01)^2)(1/n)= 40000...