The given physical quantity is

Percentage error in X is given as (∆x/x)(100)

Percentage error in a is given as (∆a/a)(100) = 1%

Percentage error in b is given as (∆b/b)(100) = 2%

Percentage error in c is given as (∆c/c)(100) = 3%

Percentage error in d is given as (∆d/d)(100) = 4%

Maximum percentage error in X = ±23.5%

X should have two significant values, therefore, X = 2.8