6. Assume that R is the region in the first quadrant (x 2 0, y 2 0) of the xy-plane whose boundary is formed by two circles x2 +y? = 1 and x2 +y? = 4 and the lines y = V3x and y = r. The change of variables r = r cos(0), y = r sin(0) (where (r, 0) are the polar coordinates) is made in order to evaluate the double integral (12 + y2 ) dA. R The correct form of the double integral is TT /3 (A) 73 drd0 TT /3 (B) , r drd0 (D) J pardo (E) none of (A) (D)