Given,
2x≤y≤4−(x−1)2:y≥0
⇒y2+(x−1)2=4 and y=2x
Now plotting the diagram we get,

Area of A: area of shaded region as shown in the above figure,
Shaded portion = circular (OABC)
−Ar(ΔOAB)=4π(4)−21(2)(1)
Hence, Area of A=(π−1)
Now, plotting the diagram of 0≤y≤min2x,4−(x−1)2 we get,

Area of B: area of shaded region as shown in the above figure,
Area of B=Ar(ΔAOB)+ Area of arc of circle (ABC)
=21(1)(2)+4π(2)2=π+1
Hence, BA=areaofBareaofA=π+1π−1