To properly consider the variability in this cost, the direct maintenance cost is considered to be a random variable following a triangular distribution with a lower limit of $215.28/m2 ($20/ft2), an upper limit of $376.74/m2 ($35/ft2), and a most probable value of $322.92/m2 ($30/ft2) [i.e., Tri(215.28, 322.92, 376.74)].