What is the oxidation state of chlorine in iron(iii) hypochlorite?

The sum of the oxidation states of the individual atoms should be equal to the the net charge of the compound /ion. 
Molecular formula of iron(III) hypochlorite is Fe(ClO)₃
This is made of a cation and anion. Cation is Fe³⁺ and anion is hypochlorite ion - ClO⁻
the net charge of the ion is -1
oxidation state of Cl - x and oxidation state of O - -2
x + (-2) = -1
x - 2 = -1 
x = -1 + 2 
x = +1
Therefore oxidation state of Cl is +1

The most plausible answer is b, duration. the given amount of time is considered how long it last for.