We know M1T1/W1 = M2T2/W2 [Identify the work here as "serving a device" and the values of this are 1 and 12 ]

Thus 700*12/1 = 1*T2/12
=> T2 = 700*12*12 seconds = 700 *12 * 12/3600 hrs =28 (OPTION B)