Question 1145449
Probability the time is under 10 minutes:
<pr>
{{{(10-12)/2}}} = {{{(-2)/2}}} = -1 
<pr>
Go to a z-table and find the value that corresponds with -1.  This value is 0.1587.  That means the probability is 0.1587 that the time required is less than 10 minutes.
<pr>
Probability the time is under 8 minutes:
<pr>
{{{(8-12)/2}}} = {{{(-4)/2}}} = -2
<pr>
Go to a z-table and find the value that corresponds with -2.  This value is 0.0228.  That means the probability is 0.0228 that the time required is less than 8 minutes.
<pr>
To find the probability that the required time is between 8 and 10 minutes, simply subtract the probability the required time is less than 8 minutes (0.0228) from the probability the required time is less than 10 minutes (0.1587).  The answer is 0.1359.