Answer:
As Per Fairchild semiconductor datasheet of 2N3904Â Â
transistor
VCE(sat) Collector-Emitter Saturation Voltage =0.2V
for IC = 10 mA
                                                                                Â
   =0.3V for IC = 50 mA
Using Point Gradient Formula
m=y2-y1/x2-x1Â Â Â Â Â Â Â Â Â Â Â Â Â
where y2=0.3 and y1=0.2
x2=50 and x1=10
Therefore m=0.0025
Similarly for IC =15mA , VCE(sat)=?
Using the above formula here y2=0.3 and
y1=unknown
x2=50 and x1=15
m=y2-y1/x2-x1
0.0025=0.3- y1/50-15
y1=0.212
therefore VCE(sat) Collector-Emitter Saturation
Voltage =0.212V for 15mA
