They would be 20, 21, 22, 23, and 24
The answer to question above is 0.0000593
Switch where the x and y are, then solve for y. f(x) = y.
x = 3y^2 + 6
x-6 = 3y^2
(x-6)/3 = y^2
f^-1(x) = y = sqrt((x-6)/3)
The first package is 4 oz (1/4lb) at 79cents = 19.75 cents/oz
Second Package is 8 oz at 1.59 = 19.875 cents / oz
So the first package is cheaper per ounce.