The answer is 30. You just multiply 51 by (10/17)
To check for continuity at the edges of each piece, you need to consider the limit as
approaches the edges. For example,

has two pieces,
and
, both of which are continuous by themselves on the provided intervals. In order for
to be continuous everywhere, we need to have

By definition of
, we have
, and the limits are


The limits match, so
is continuous.
For the others: Each of the individual pieces of
are continuous functions on their domains, so you just need to check the value of each piece at the edge of each subinterval.
Answer:

The degrees of freedom are given by:
Now we can calculate the p value with the following probability:

And for this case since the p value is lower compared to the significance level
we can reject the null hypothesis and we can conclude that the true mean for this case is different from 30.6 at the significance level of 0.05
Step-by-step explanation:
For this case we have the following info given:
represent the sample mean
represent the sample deviation
represent the reference value to test.
represent the sample size selected
The statistic for this case is given by:

And replacing we got:

The degrees of freedom are given by:
Now we can calculate the p value with the following probability:

And for this case since the p value is lower compared to the significance level
we can reject the null hypothesis and we can conclude that the true mean for this case is different from 30.6 at the significance level of 0.05