what statistic should be used? What is the value of that calculated statistic?    Please explain!

The variable should be measured is increase in knowledge after the students participated in an awareness program .

Given that 

Sample Size, n=25

Population mean,$\mu$ =35

Population standard deviation,$\sigma$=5

Sample mean,$\overline{x}$ =40

Sample standard deviation,s=10

use  z test statistic, since the population standard deviation is known even though the sample size is small.

The null hypothesis is,

H0:$\mu$ <=35

The alternative hypothesis Is,

Ha:$\mu$ >35