You must know that the company is able to deliver only 90% of manufactured pens. So let k be the manufacturing price of a pen, then
Total income (including 25% profit) = 8000 x k x 1.25
Also this same income is obtained by selling 90% manufactured at Rs.10 which is equal to 7200 x 10.
Thus 8000 x K x 1.2 = 7200 x 10
⇒ K = Rs. 7.2 ( 90% of 8000 = 7200)
