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