Josephine is constructing an open box by cutting the squares off the corners of a sheet of paper sized 20cm by 16cm. She is considering options of 3cm, 4cm and 5cm squares in order to maximise the volume of the box.
a) Develop the volume function based on the information provided above.
b) Calculate the volume of the box when she cuts off 3cm, 4cm and 5cm squares.
c) Use your knowledge of polynomials and help Josephine determine which the best solution is. Which option would provide the box with the maximum capacity and what is the volume of the box? Explain in details!