(g) Implement these two optimisations to the concat function (you might want to make a new version). You can use a function isShort(s: String): bool to represent the “shortness” criterion; if your tool supports it you don’t need to give the function a body. In other words, the function can be uninterpreted: your verification can be agnostic as to what counts as “short” (that’s up to the function). 