contestada

A sample of milk is found to have arsenic at a concentration of 1.31 µg/l (microgram/liter). What is the concentration in ounces per gallon?
a) 3.90 × 10⁻⁷ oz/gal
b) 1.31 × 10⁻⁶ oz/gal
c) 4.95 × 10⁻⁶ oz/gal
d) 1.31 × 10⁻³ oz/gal