In python write a function called numbers that has 4 parameters

In python write a function y with 4 parameters (a, b, c, d) The parameter a is the being evaluated The function should return a floating-point value. a-b if b= d it should return something like this: >>> y(5,v10, 15, 20) 0.0 >>>y(50, 40, 80, 100) 0.3 >>>y(60, 20, 60, 100) 1.0 >>> y(80, 50, 75, 100) 0.8 >>>y(100, 40, 70,90) 0.0