The oil slick thick = 1.256 x 10⁻⁴ cm
Volume is a derivative quantity derived from the length of the principal
The unit of volume can be expressed in liters or milliliters or cubic meters
The conversion is
1 cc = 1 cm3
1 dm = 1 Liter
1 L = 1.06 quart
so for 1 quart = 0.943 L
[tex]\tt 0.943~L=0.943\times 10^{-3}m^3[/tex]
Volume of oil dumped = volume of swimming pool
[tex]\tt 0.943\times 10^{-3}~m^3=25\times 30\times h(h=thick)\\\\h=\dfrac{0.943\times 10^{-3}}{750~m^2}=1.257\times 10^{-6}~m=\boxed{\bold{1.256\times 10^{-4}~cm}}[/tex]