(a) compute the ratios of assessed valuation to the full valuation of
taxable real estate on the basis of market value surveys completed
pursuant to article twelve of this chapter;
(b) on the basis of the ratios computed pursuant to subdivision (a) of
this section, project increases or decreases in the ratios for years for
which the information has not been developed pursuant to article twelve
of this chapter;
(c) avail itself of appropriate market value information appearing in
its office or acquired in the discharge of its duties pursuant to this
chapter.