What would be the runtime in big O notation for a singly linked list implementation $($with last pointer$)$ of a stack for: a$.$ Push $($where the $$top$$ of the stack is the end$/$last of the stack$)$ b$.$ Pop $($where the $$top$$ of the stack is the end$/$last of the stack$)$ c$.$ Push $($where the $$top$$ of the stack is the front$/$head of the stack$)$ d$.$ Pop $($where the $$top$$ of the stack is the front$/$head of the stack$)$