(a) The diameter of cylindrical water reservoir is
and its height is 45.54 m.
Radius of cylinder is half of its diameter thus,

Volume of cylinder can be calculated as follows:

Here, r is radius and h is height, putting the values,

Since,

Thus, volume will be

The concentration of fluoride
is approximately 1 ppm.
Since, 1 ppm=1 mg/L
thus,

Mass can be calculated as follows:
m=C×V=

Therefore, mass of fluoride will be
.
(b) In NaF, sodium and florine are present in 1:1 ratio thus, 1 mole of fluoride gives 1 mole of NaF.
Mass of fluoride is
and its molar mass is 19 g/mol thus, number of moles will be:

Thus, number of moles of NAF formed will be

Molar mass of NaF is 41.98 g/mol, mass can be calculated as follows:
.
Therefore, grams of NaF containing this much of fluoride is
.