firstly Ashish is studying chemistry and sitting at the third position to the left of ruby so fix one position for Ruby and place Ashish according to that and kartik is sitting on the same side of Ashish.
Step II: Rocky is the neighbour of Ashish and Nitish is sitting between Ruby and Saina and study Economics so according to that the arrangement will be: 
Step III: Saina study Maths and sits second to the left of Rocky who study computer science. 
Step IV: The neighbour of Kartik study English and Ashish already study chemistry so the person sitting to the immediate right of Kartik will be studying English. 
Step V: Harsh study Hindi and there is only one position vacant which is to the immediate right of Saina so Harsh will be sitting there and the remaining subject is physics so Kartik will be studying that subject and the person remaining is Aman so he will be siting with Ruby and will study English. Here CS=computer science. 
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