Calculate the initial concentration of Fe₃ in a mixture prepared by combining the following solutions: 7.50 ml of 0.00200 M Fe(NO₃)₃ and 2.50 ml of 0.00200 M KSCN.
a) 0.00125 M
b) 0.00200 M
c) 0.00250 M
d) 0.00400 M