please help with hw

The currents I1 , I2 , 13 in a circuit with resistors R1, R2 and voltages E1 , E2 are described by the following system of equations: R111 + R313 = E1 R212 + R313 = E2 11 +12 I3 = 0 Let R1 = 2 Ohms, R2 = 1 Ohm, R3 = 4 Ohms, E1 = 14 Volts and E2 = 28 Volts. 2 o 4 11 14 0 1 4 I2 28 A: 1 1 1 X: I3 B: 0 (3a) Given AX = B, find det(A). (3b) Given AX = B, find I1 using Cramer's Rule