Write formal for the following informal specifications. In each case the signature is {x N, x' N}. Use angle bracket notation.

(a) x' is bigger than x.

(b) x' twice as big as x if x is smaller than 100; otherwise it doesnt matter what x' is.

(c) x' twice as big as x if x is smaller than 100; otherwise x' is 200.

(d) x is at least 1 and x' is smaller than x.