The temperature in a bank vault is normally distributed with mean 10C, and standard deviation 2C. A team of thieves has a plan to drill into the vault, but while doing so they will raise the temperature to a constant 10.2C. The temperature is automatically checked by a computer every minute which carries out a hypothesis test on the average temperature so far that day to see if it has risen, with a 10% significance level. If it detects a statistically significant change it calls the police automatically. Find how many minutes the thieves will have before the alarm is triggered