The Poynting vector S⃗ S→S_vec gives the energy flux per unit area of electromagnetic waves. It is defined by the relation S⃗ =E⃗ ×B⃗ μ0S→=E→×B→μ0. Calculate the time-averaged Poynting vector ⟨S⃗ ⟩⟨S→⟩ of the wave considered in this problem.

Assume you measured the mass of the cart to be (500 ± 1) g and the mass of the additional mass you put on the cart to be (500 ± 1) g as well. since the scale you are using in the lab cannot measure objects heavier than 600g you will have to sum up individual pieces and propagate the error. so what would be the mass and the standard error of the cart and the mass