Identify the substance oxidised, reduced, oxidising agent and reducing agent for each of the following reactions :
a) `2AgBr(s)+C_(6)H_(6)O_(2)(aq)to2Ag(s)+2HBr(aq)+C_(6)H_(4)O_(2)(aq)`
b) `HCHO(l)+2[Ag(NH_(3))_(2))^(+)(aq)+3OH^(-)(aq)to2Ag(s)+HCOO^(-)(aq)+4NH_(3)(aq)+2H_(2)O(l)`
c) `HCHO(l)+2Cu^(2+)(aq)+5OH^(-)(aq)toCu_(2)O(s)+HCOO^(-)(aq)+3H_(2)O(l)`
d) `N_(2)H_(4)(l)+2H_(2)O_(2)(l)toN_(2)(g)+4H_(2)O(l)`
e) `Pb(s)+PbO_(2)(s)+2H_(2)SO_(4)(aq)to2PbSO_(4)(s)+2H_(2)O(l)`