Volume of the rectangular prism ==> V=7x4x10 ==>280 dm³
We know that 1 Liter (of mass) correspond to 1 dm³ in volume,
So, the number of liters = to 10,690.4 Liter OR 10,690.4 dm³
Hence we can apply the formula Density =L/V
D=10,690.4/280==> D=38.18 L/dm³