Answer:
The mean of depth is 12.75cm.
The variance of depth is of 13.02 cm².
Step-by-step explanation:
An uniform probability is a case of probability in which each outcome is equally as likely.
For this situation, we have a lower limit of the distribution that we call a and an upper limit that we call b.
The mean of the uniform distribution is:

The variance of the uniform distribution is given by:

Uniform distribution on the interval (6.5, 19)
This means that: 
So
Mean:

The mean of depth is 12.75cm.
Variance:

The variance of depth is of 13.02 cm².