Write a method called Input that has four double parameters x1, x2,x3, and x4. The method should accept double numbers from the keyboard. Write another method name product, the method should find the...

Write a method called Input that has four double parameters x1, x2,x3, and x4. The method should accept double numbers from the keyboard. Write another method name product, the method should find the product of the numbers that have been accepted from the user.