An npn differential amplifier with I = 0.5 mA, Vcc = VEE = 2.5 V, and Rc = 8 kohm utilizes BJTs with B=100 and VBE=0.7 V at Ic = 1 mA. Assuming that the bias current is obtained by a simple current source and that all transistors require a minimum VCE of 0.3 V for operation in the active mode, find the input common-mode range.