A data scientist aims to develop a neural network model to predict whether a customer will be interested in a new product. Each customer record contains the following attributes: Age $($ranges from $20$ to $70),$ Ethnicity $($possible values are White, Asian, Black, Hispanic, Others$),$ Annual Income $($ranges from $20000$ to $500000),$ Whether he$/$she is a new customer $($possible values are Yes. No$).$ Which of the following encoding operations is NOT NEEDED?

$$a$)$ One$-$hot encoding on 'Ethnicity

$$b$)$ One$-$hot encoding on 'Whether he$/$she is a new customer

$$c$)$ Min$-$Max normalization on 'Annual Income'

$$d$)$ Min$-$Max normalization on 'Age'