Atomic weight of an element X is 120 when one amu is defined as `1//18th` part by weight of an element of `C^(12)`. On the same scale, atomic weight of another element Y is 72. Which of the following statement regarding X and is (are) correct?
a. On conventional scale, atomic weight of X is 80
b. On conventional scale, atomic weight of Y is 108
c. On a scale when an amu is defined to be `1//30th` of the weight of an atom of `C^(12)`, atom of `C^(12)`, atomic weight of X 200
d.On a scale when an amu is defined to be `1//15th` of the weight of an atom of `C^(12)`, atomic weight of Y is 90