(b) Researchers have designed a graphene field-effect transistor, where graphene-oxide is used as the transistor channel between the source and drain electrodes. Explain how such a sensor configuration could be used to detect the presence of specific single stranded DNA molecules in the solution. [4] (c) Explain how the same measurement could be performed with an amperometric biosensor, taking care to specify the difference between the two types of electrochemical sensors. [7]