In measuring the resistance R (Ω) of a carbon-filament lamp at various voltages (V) the following results were obtained:
V(volts) 60.0 70.0 80.0 90.0 100 120
R(Ω)
70.0 67.2 65.0 63.4 62.1 60.0
Plot a suitable straight-line graph given that the law connecting R and V is of the form R = Va + b .