<Li> The Birket <Ul> <Li> River Fender <Ul> <Li> Prenton Brook </Li> </Ul> </Li> <Li> Arrowe Brook <Ul> <Li> Greasby Brook <Ul> <Li> Newton Brook </Li> </Ul> </Li> </Ul> </Li> </Ul> </Li> <Ul> <Li> River Fender <Ul> <Li> Prenton Brook </Li> </Ul> </Li> <Li> Arrowe Brook <Ul> <Li> Greasby Brook <Ul> <Li> Newton Brook </Li> </Ul> </Li> </Ul> </Li> </Ul> <Li> River Fender <Ul> <Li> Prenton Brook </Li> </Ul> </Li> <Ul> <Li> Prenton Brook </Li> </Ul>

What is the width of the river mersey