<PRE><B>Question 1120530</B>
a.  6 trials or n. p=0.250 q=0.750
b.  4 hits is 6C4 or 15 ways that can happen*0.25^4*0.75^2,=0.0330.
5 hits is 6*0.25^5*0.75 or 0.0044
6 hits is 0.25^6 or 0.0002
At least 4 hits is that sum or 0.0376 or round to 0.038

Want the z score for this where z=(x-mean)/sd
z is between (20-23.5)/10 or -0.35 and +0.15
That probability is 0.1964
z(0.80)=+0.842
0.842=(x-mean)/sd
8.42=x-mean
x=31.92 mpg</PRE>