E) 12 minutes
A normal curve has approximately 95% of graph between mean - 2sd and mean + 2sd
So 95% of the times will be between 0 and 12 minutes. 6 - 2x3 to 6 + 2x3
2.5% will take over 12 minutes
Strangely 2.5% will also take less than 0 minutes to process which shows the normal curve is not perfect in this example.
You can use trigonometry specially the cos rule in this case. I can’t send the other pictures. But using the cos rule you can check whether the angle is 90
