When an object is kept at a distance of 30 cm from a concave mirror, the image formed is at a distance of 10 cm. If ________.

a) the object is moved closer to the mirror, the image moves away from the mirror
b) the object is moved closer to the mirror, the image moves closer to the mirror
c) the object is moved away from the mirror, the image moves closer to the mirror
d) the object is moved away from the mirror, the image moves away from the mirror