Question 1089939
The mean is 30K with sd of 5 K
z=(x-mean)/sd, and this is a z of +/-1
That is 68% of them or 680 cars.
Between 30 and 40 K is between 0 and 2 sds
But 96% applies to +/- 2 sd s so 48% between 0 and 2 sd s and 48% between 0 and -2 sd s.  Only the first 48% applies.  That is 480 cars.