A student performed the experiment of determining the focal length of a concave mirror by the u-v method using an optical bench of length 1.5 m. The focal length of the mirror used is 24 cm. The maximum error in the location of the image can be 0.2 cm. The 5 sets of (u, v) values recorded by the student (in cm) are : (42, 56), (48, 48), (60, 40), (66, 33), (78, 39). The data set(s) that cannot come from the experiment and is (are) incorrectly recorded, is (are) :

(a) (42, 56)

(b) (48, 48)

(c) (66, 33)

(d) (78, 39)