Determine the region of operation for the following transistors: a. npn , VBE= 0.8 V, VCE= 0.4 V b. npn , VCB= 1.4 V, VCE= 2.1 V c. pnp , VCB= 0.9 V, VCE= 0.4 V d. npn , VBE= -1.2 V, VCB= 0.6 V