First, we have to find the z scores of $4 and $9.50.
Z₁ = ($4 - $6.50)/$2.25 = -1.11
Z₂ = ($9.50 - $6.50)/$2.25 = 1.33
Then, using a z score table, we find the probability of 1.33 and -1.11, and subtract them to determine the probability in between.
0.9082 - 0.1335 = 0.7747 or 77.47%.
I think the answer might be c
