Given that the cubical piece has side (s) 7 mm, and a cylindrical hole of diameter (d) as 3 mm.
The volume of the piece can be calculated as,

It is mentioned that the material costs $207 per cubic meter, so the cost (c) of 1 piece is calculated as,

This is the cost (in dollars) for 1 piece.
Given that the manufacturer wants to produce 1,000,000 such pieces, so the total cost (TC) is calculated as,

Thus, the total prototypes will cost around $60.75
G^2+2=0,
g^2=-2
g= sqrt-2, not possible.
3g+1=0
3g=-1
g=-1/3
9 cannot be equal to zero for the last one.
He saved 30 dollars through babysitting. My math is:
84 / 14 = 6
6 x 5 = 30
I hope this helps!