If the costs of completion of a building are normally distributed with a mean of $700,000 and a standard deviation of$150,000, what are the chances of making a profit if the promised return is $1,000,000 and how much has to be obtained in order to have a 90% chance of making a profit? Cheers for any tips. 2. Ok, it seems you should find a z-score here. $\displaystyle z=\frac{x-\mu}{\sigma} =\frac{x-700000}{150000}$ Now is the 1000000 also a building cost? if so make it $x$ in the above equation. 3. Nah, the$1bn is not the building cost, it's supposed to be expected profit which confuses me quite alot