Answer:
 
    
The degrees of freedom are given by:
 
  
And the p value would be:
 
    
Since the p value is lower than the significance level we have enough evidence to conclude that the true mean for this case for the growth rate is less than 2cm per week
Step-by-step explanation:
Information given
 represent the sample mean for the growth
 represent the sample mean for the growth
 represent the sample standard deviation
 represent the sample standard deviation    
 sample size
 sample size    
 represent the value that we want to compare
 represent the value that we want to compare
 represent the significance level
 represent the significance level
t would represent the statistic    
 represent the p value
 represent the p value
System of hypothesis
We need to conduct a hypothesis in order to check if the true mean is less than 2cm per week, the system of hypothesis are :    
Null hypothesis: 
    
Alternative hypothesis: 
    
Since we don't know the population deviation the statistic is given by:
 (1)
 (1)    
Replacing the info given we got:
 
    
The degrees of freedom are given by:
 
  
And the p value would be:
 
    
Since the p value is lower than the significance level we have enough evidence to conclude that the true mean for this case for the growth rate is less than 2cm per week