a$)(2$ pts$)$ Given two sorted singly linked lists, define a method merge that merges the given lists into a third one that will also be sorted and contains the duplication of the elements.For example, if the first list contains $\{1,2,2,4,6),$ and the second contains $(2,6,7),$ the result should be $\{1,2,2,2\mathrm{.}4\mathrm{.}6,6,7\}.$If one of the given lists is empty, your method should return the head reference of the other list.Possible header:public static NODE merge$($NODE headi, NODE head$2)(//$head and head$2$ are the heads' references to I$/$the first and the second lists respectivelyb$)(0\mathrm{.}5$ pt$)$ Determine the time complexity of your method using the Big$-$Theta notation in terms of m and n$,$ the lengths of the lists.