Hausdorff dimension of sets

What is the Hausdorff dimension of the following sets?

a) { (x,x) http://upload.wikimedia.org/math/7/b...e1a4c7cff0.png R^2 : x http://upload.wikimedia.org/math/7/b...e1a4c7cff0.png Q } where R is the real numbers and Q is the rational numbers.

b) { (x,x)http://upload.wikimedia.org/math/7/b...e1a4c7cff0.png R^2 : xhttp://upload.wikimedia.org/math/7/b...e1a4c7cff0.png R }

c) { (x,x)http://upload.wikimedia.org/math/7/b...e1a4c7cff0.pngR^2 : xhttp://upload.wikimedia.org/math/7/b...e1a4c7cff0.png C } where C is the middle third cantor set.

I think the answer to c) is log2/log3 but i am not sure how to find the other two Hausdorff dimensions.

Thanks.