Correct Answer: b) 40 degrees

We know that STVW is a square. Let us assume that side of square is x
=> VW = x -------------->(1)
We are given that UW = 2UV -------------------------> (2)
Consider triangle UVW, Angle V is 90 degrees
=> UW^2 = UV^2 +VW^2
=> From (2) and (1),
(2UV)^2 = UV^2 +x^2
=> 4UV^2 - UV^2 = x^2
=> 3UV^2 = x^2
=> UV = x/√3

Now, given that UW = 2UV = 2X/√3
Consider that UV:VW:UW = x/√3 : X : 2X/√3
= 1 : √3. : 2
=> UVW is 30-60-90 triangle. => Angle VUW. = 60
Angle VWU = 30
This means that 3a = 30 = 90
=> 3a = 60
=> a =20

Since SX and YZ intersect at point W, Angle ZWS = Angle XWY
=> B = 2a
=> b= 40 degrees