Assume the printercartridgesin average can print 12,000 pages with 800 pages as its standard deviation (= 12000, = 800), and it is a bell-shaped distribution for the number of pages (X) it can print before running of of ink.(X is a random variable, isn't it?)

What is the chance that your cartridge can print between11,245 to 13,654 pages?That means in Math: P(11,245 < X < 13,645)?

Four decimals.