Calculate the quantity indicated for each of the following electrolyses.

(a) [Cu²⁺] remaining in 425 mL of a solution that was originally 0.366 M CuSO₄, after passage of 2.68 A for 282 s and the deposition of Cu at the cathode; 

(b) The time required to reduce [Ag⁺] in 255 mL of AgNO₃(aq) from 0.196 to 0.175 M by electrolyzing the solution between Pt electrodes with a current of 1.84 A.