we need to calculate a z-score and refer to the normal distribution tables.
Remember that not all distribution tables read the same way, but they should show you by a diagram whether the percentage given is for the area to the left of the z or to the right.
Z = (X - μ)/σ or Z = (.8543 - .8605)/.0513 = -.1209
The area to the right of this Z-score translates to a probability of 0.5478