For an erect (that is, upright) and virtual image and 2.5x Magnification,
build from "Absolute Value Of The Ratio Of Image Distance To Object
Distance Equals Magnification." the Equation |q/0.24| = 2.5.
This translates to q = -2.5p or -2.5(0.24 meters) equal to -0.6 meters.
Focal Length or f is determined next from 1/(0.24) + 1/(-0.6) = 1/f; this gives
f as 0.4 meters.
Finally take Radius Of Curvature or R as 2f or 2(0.4 m) or 0.8 meters.
