Answer:
b. -0.862
Explanation:
The only answer choice with a minus sign is B, which is the correct choice.
When the value of interest is below the mean (2800 is below 3550), the z-score will be negative:
z = (2800 -3550)/870 = -750/870 ≈ -0.86207 ≈ -0.862
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As always, z is computed as ...
Z = (X -μ)/σ