If the cost of $1kg$ of fish is $₹200$. Salman sells $5kgs$ of fish at $₹300$ per kg, how much profit has he earned?

The correct option is (B),
Given the cost of $1kg$ of fish $=₹200$
Given the selling price of $1kg$of fish $=₹300$
He sells $5kgs$ of fish
Cost of $5kgs$ of fish
$$\begin{gathered} =200\times 5 \\ =1000 \end{gathered}$$
The selling price of $5kgs$ of fish
$$\begin{gathered} =300\times 5 \\ =1500 \end{gathered}$$
Profit earned by selling fish
$$\begin{gathered} =1500-1000 \\ =500 \end{gathered}$$
Therefore, he earns a profit of $₹500$ by selling $5kgs$ of fish.