Answer:
q = 42.3 x 10⁻³ C = 42.3 mC
Step-by-step explanation:
in order for the Sulphur charge to float the weight of the charge must be equal to the electric force:

where,
q = charge required = ?
W = Weight = 7.4 N
E = Electric Field Strength = 175 N/C
Therefore,

q = 42.3 x 10⁻³ C = 42.3 mC