I'm new to this forum and I have been struggling with this questiong for a while:

Imagine you are building a wall from precast concrete blocks. Standard 20 cm Blocks are 19.5 cm high to allow for a 0.5 cm layer of mortar. In practice, the height of a block plus mortar row varies according to a Normal Distribution with mean 20.0 cm and standard deviation 0.25 cm. Heights of successive rows are independent. Your wall has 10 rows.

(i) What is the distribution of the height of the wall? ( 3 marks)

(ii) What is the probability that the height of the wall differs from the design height of 200 cm by more than 1 cm? ( 4 marks)

I'm just really confused about how to approach it.

Because it is a sample of 10 from a normal distribution, can you apply the t distribution with sample mean 20.0cm and sample stdev. 0.25cm?

From this, I'm not quite sure how to approach part (ii)

Any guidance would be greatly appreciated.