I am reading through a book which provides an example of a linear program given by \begin{align}\min&\quad-24y_{1}-28y_{2}\\\text{s.t.}&\quad6y_{1}+10y_{2} \leq 2400\\&\quad8y_{1}+5y_{2} \leq 1600\\&\quad0\leq y_{1} \leq 500\\&\quad0\leq y_{2} \leq 100.\end{align}
The solution is $-6100{\rm(objective\ value)}, y^{\top} = (137.5,100), \pi^{\top} = (0,-3,0,-13)$ where $\pi$ is the simplex multiplier associated with the solution.
I can solve the LP to find the feasible values of $y$ but I do not understand how to find the values of the simplex multiplier. Reading some papers I found out that the simplex multiplier is calculated as:
$$\pi^{\top} = c_{B}^{\top} B^{-1}.$$
I have attempted to use this by writing this LP in the standard form but I cannot match the values of the $\pi$: \begin{align}\min&\quad C^\top X\\\text{s.t.}&\quad A\cdot X=b\\&\quad A = \begin{pmatrix} 6 & 10 & 1 & 0 & 0 &0 \\ 8 & 5 & 0 & 1 & 0 &0\\ 1 & 0 & 0 & 0 & 1 &0\\ 0 & 1 & 0 & 0 & 0 &1 \end{pmatrix}\\&\quad b = \begin{pmatrix} 2400 \\ 1600 \\ 500\\ 100 \end{pmatrix}\\&\quad c = \begin{pmatrix} -24 \\ -28 \\ 0\\ 0\\ 0\\ 0 \end{pmatrix}\\&\quad B = \begin{pmatrix} 1 & 0 & 0 &0 \\ 0 & 1 & 0 &0\\ 0 & 0 & 1 &0\\ 0 & 0 & 0 &1 \end{pmatrix}\quad{\rm(Basis\,Matrix)}.\end{align}
Can anyone please explain how to calculate the simplex multiplier in this example?