AP(492 < x-bar < 512)
z = (492-502)/100/√90
z = -0.95 is 0.1711
z = (512-502)/100/√90
z = 0.95 is 0.8289
b. P(505 < x-bar < 525)
z = (505-515)/100/ √90
z = -0.95
z = (525-515)/100/ √90
z = 0.95
P(-0.95< z < 0.95) = 0.6578
P(-0.95< z < 0.95) = 0.6578
c. P(484 < x-bar < 504)
z = (484-494)/100/√100
z = -1 is 0.1587
z = (504-494)/100/√100
z = 1 is 0.8413
P(-1< z <1) = 0.6826