 Solution

Use the line fraction occupied by the tall narrow ridges as an estimate of cementite volume fraction, assuming the line is representative and its etched height classification identifies the phases correctly. The displayed profile gives roughly $17vol\%$ cementite and $83vol\%$ ferrite.

An operational measurement at a height threshold near $75\mathrm{nm}$ gives four ridge widths totaling about $0.88\mu \mathrm{m}$ over a profile about $5.3\mu \mathrm{m}$ long:Changing the threshold over a reasonable part of the high ridges gives roughly $16$–$18\%$, so this is an image-based estimate, not an exact phase analysis. The occasional low protrusions should not all be counted as full cementite lamellae merely because they are above a noisy baseline. The reference line and threshold convention must be stated.