Add a method
LispList merge(LispList other)
to the LispList interface of Exercise P15.10 that returns the length of the list. Implement the method in the EmptyList and NonEmptyList classes. When merging two lists, alternate between the elements, then add the remainder of the longer list. For example, merging the lists with elements 1 2 3 4 and 5 6 yields 1 5 2 6 3 4.