Explanation

This uses the empirical mode–median–mean relation for moderately asymmetrical distributions: mode = 3·median - 2·mean. Substituting: 3 × 220 - 2 × 270 = 660 - 540 = 120. Note this is an empirical approximation, not an exact identity — but it is the standard formula CDS tests here. Option (b) 220 confuses mode with median. Hence option (a).