We know, dipole moment is a vector quantity
Let the dipole moment of OH bond be x D.
Using formula
R = √P2+Q2+2PQcosθ
where R is the resultant dipole moment
P = Q is the dipole moment of each OH bond
put up values,
R = √x2+x2+2x2cos104o
⇒1.85=√2x2−2x2×0.25
⇒1.85=√1.5x2
⇒3.4225=1.5x2
On solving, x = 1.51 D