SOLUTION: For a standard normal distribution, find: P(-0.4 < z < 2.26)

This probability is the area under the normal curve 
between the assigned raw marks.


Use your graphing calculator, like TI-83 or TI-84.


Its standard function normalcdf calculates what you need.


normalcdf is the  " Normal Cumulative distribution function ".

The format of this function is normalcdf(low mark, high mark, mean, SD).

                           P = normalcfd(-0.4,     2.26,      1,    0)


Alternatively, you may use free of charge online calculator at this web-site

https://onlinestatbook.com/2/calculators/normal_dist.html


It shows the shaded are of interest, so you clearly see what you are doing
and can understand what is going.  It prevents you of making errors.


If you are a novice in such calculations, I recommend you to start
with the online calculator and then to switch to the graphing calculator.