In the following number series one term is wrong and another term is missing. If the wrong term is X and missing term is Y, find the ratio of X : Y.
1215, 1216, 1220, 1247, 1603, Y
1
1503 : 4628
2
4628 : 1503
3
4628 : 1603
4
1603 : 4628
5
None of these.