From the question,
Rohan bought an almirah for =Rs.13600= cost price
Transportation cost =Rs.400
The total cost price of almirah =Rs.(13600+400)
The total cost price of almirah =Rs.(13600+400)=Rs.14000
He sold it for =Rs.16800= selling price
By comparing SP and CP=SP>CP, so there is a gain
Gain=SP−CP
=16800−14000
=Rs.2800
Gain %={(gain/CP)×100}
={(2800/14000)×100}
={2800/140}
=20%