A student measured the diameter of a small steel ball using a gauge of least count 0.001 cm. The main scale reading is 5 mm and zero of circular scale division coincides with 25 divisions above the reference level. If gauge has a zero error of -0.004 cm. the correct diameter of the ball is
(a) 0.521 cm
(b) 0.525 cm
(c) 0.053 cm
(d) 0.529 cm
