here is the solution

but i really can't understand why prb(z=-1) is 0.0833

i thoguht its 0.1587 since z=1 is 0.1587

can you explain me

Store A uses the newsvendor model to manage its inventory. Demand for its product is normally distributed with a mean of 150 and a standard deviation of 60. What its expected inventory if Store A's order quantity is 90 units? z = (90-150)/60 = -1, Probability (z=-1) = 0.0833, Expected Inv (expected number of units not sold at the end of the season) = std * probability = 5 C