You're expected to know (or find out eg. Variance - Wikipedia, the free encyclopedia) that ~ .
Use this to answer the second part of your question.
If is the variance of a random sample which is drawn from a normal distribution then has a standard distribution for a particular value of the constant c.
Specify the constant c. What is the distribution?
How many pairs of positive constants a; b exist such that ?
You're expected to know (or find out eg. Variance - Wikipedia, the free encyclopedia) that ~ .
Use this to answer the second part of your question.