Having some trouble deriving the answer for the below question from my Aerocourse workbook regarding pressurization .... if anyone could please help with an explanation as to your answer would be appreciated

It reads :

The pressurization system of a large commuter turbo prop has been given a maintenance release for the auto mode part of the system provided it is operated in the manual mode only . What cabin altitude would you select if flight planned cruise is 16000 ft and want to obtain maximum aircraft differential ?

a. 8000
b. 4000
c. 2500
d. 500 ft above elevation

Answer C

Find 16,000 feet on the horizontal scale of the chart. Then go up until you touch the solid line "Maximum Pressure Differential Schedule 5.5 PSI" Once you are at the intersection of 16,000 and the black solid line move across the chart horizontally to read the altitude in the vertical scale.

Hope I explained it alright!

Thanks Torresdenochea .... that explains it perfectly !

You are welcome, good luck!