A point P lies inside the circles x2+y2−4=0 and x2+y2−8x+7=0. The point P starts moving under the conditions that its path encloses greatest possible area and it is at a fixed distance from any arbitrarily chosen fixed point in its region. The locus of P is
a. 4x2+4y2−12x+1=0
b. 4x2+4y2+12x−1=0
c. x2+y2−3x−2=0
d. x2+y2−3x+2=0