Two things need to give attention in this question, First we need to calculate gain for 1 year only.
Second, where we take money at some interest and lends at other, then we use to subtract each other to get result in this type of question. Lets solve this Simple Interest question now.
Gain in 2 year = − = 625 − 400 = 225 So gain for 1 year = = 112.50