Three gears, A, B , and C , mesh with each other in a motor assembly. Gear A has a radius of 4 in., B has a radius of 3 in . , and C has a radius of 1 in . If the largest gear is centered at (-7,0) , the smallest gear is centered at (4,0) , and Gear B is centered at the origin, what is the equation of each circle in standard form?