Question 973522
Radius of the circle=x+4y
Area of the outermost ring=Area of the circle-Area of the penultimate ring
                          =π(x+4y)^2-π(x+3y)^2
                          =π(x^2+8xy+16y^2-x^2-9y^2-6xy)
                          =π(2xy+7y^2)