Final answer:
Vance should have found the intersection of two angle bisectors of triangle LMN instead of two altitudes.
Step-by-step explanation:
The part of Vance's plan that requires revision is option B: Vance should have found the intersection of two angle bisectors of triangle LMN instead of two altitudes.
When constructing a circle tangent to all three sides of a triangle, the circle should be centered at the incenter of the triangle, which is the intersection point of the angle bisectors of the triangle. The altitudes are not used in constructing this circle.
The correct steps to construct the circle would be to find the intersection of the two angle bisectors of triangle LMN and then draw a circle centered at that intersection point to pass through point P.