Calculate the indicated Riemann sum S₄ for the function f(x) = 26 – 2x². Partition [0,12] into four subintervals of equal length, and for each subinterval [Xₖ₋₁,xₖ], let Cₖ = (xₖ₋₁ + 2Xₖ) /3.

S₄ = ___ (Simplify your answer.)