class Vehicle1:
    def __init__( self, color, price, wheels):
        self.color=color
        self.price=price
        self.wheels=wheels
        #self.speed=speed
    def set_speed(self, speed = 100):
        self.speed=speed
    def accelerate(self, amount) :
        self.speed += amount
        return self.speed
    def decelerate(self, amount) :
        self.speed -= amount
        return self.speed

   
betty=Vehicle1("yellow", 2000.00, 4)
betty.set_speed()
betty.accelerate(10)
print "new speed = ", betty.speed 
betty.decelerate(20)
print "new speed = ", betty.speed