Question: The joint density function for Y₁, the weight in tons of a bulk item stocked by a supplier, and Y₂, the weight of the item sold by the supplier, has joint density

f(y₁,y₂)= 1/y₁, 0 ≤ y₂ ≤ y₁ ≤ 1,

In this case, the random variable Y₁ –Y₂ measures the amount of stock remaining at the end of the week, a quantity of great importance to the supplier. Find E(Y₁ –Y₂).