Identify (E) and (F) in the following:
FeSO4 (A) Δ→ (B) + (C) + (D)
(C) and (D) are gases, (B) is red-brown solid, (C) can be oxidised to (D). (C) also turns Cr2O2−7/H+ solution green. (B) dissolves in HCl forming deep yellow solution (E). (E) gives blue colour (F) with K4[Fe(CN)6]. (D) dissolves in H2O forming a well knows mineral acid called "king of acids".