How to implement this in C# ?

Question

Add new functionality according to the following specification. A private patient, according to his/her policy, is able to receive a discount from the Doctor's fee. These discounts are: Level A – 10% Level B – 20% Level C – 30% Implement functionality that enables the Doctor's fee to be calculated according to the above requirements. Note a public patient gets no discount.

// for reference you can use these