Ans will be 1073
The main point of question is , without the $1$st and last row - all other row contains 3 elements
Now, the matrix contains $50\times 50$ elements.
So, finding $P\left [ 25,26 \right ]$ not a last element of the matrix. We only have to consider $1$ st row with $2$ elements. Other all rows with $3$ elements
Now for $P\left [ 25,26 \right ]$ it will be $2+3\times 24=1074$
But here array start with $1000$
So, address of $P\left [ 25,26 \right ]$ will be $1$ less, i.e. $1073$