4. The yield, in bushels per acre, of a certain type of feed grain in the midwest can be represented as the outcome of the random variable Y defined by Y ¼ 3x:30 l x:45 k eU where xl and xk are the per acre units of labor and capital utilized in production, and U is a random variable with probability density function given by fðuÞ ¼ 2e2uIð Þ 0;1 ðuÞ