For a standard normal distribution, which of the following expressions must always be equal to 1?
pzs-a) - p(-aszsa) - p(z2a)
pizs-a) - p(-aszsa)+ p(z? a)
o p(zs-a)+ p(-aszsa)- p(zea)
p(zs-a)+p(-aszka)+p(728)

Planet earth has a mass of 5.9726x10²⁴ kg.then: 5.9726x10²⁴ kg=100% of the total earth mass.if the water´s mass=5x10-4 % of the total mass, we can solve this problem by the rule of three.5.9726x10²⁴ %*10⁻⁴ %x=(5.9726x10²³ kg)(5*10⁻⁴  %) / 100 %=2.9863x10¹⁹ kganswer:   the mass of the planet´s water would be   2.9863 x 10¹⁹ kg.