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\begin{aligned} & For \, Cost \, Buffer \\  &B_{C-P}=.5 \times \sum\nolimits_{i=1}^{N}\left(C_{p}-C_{m}\right)=\$ 90060 \\ &B_{r s e}=\sqrt{\sum\nolimits_{i=1}^{N}\left(C_{p}-C_{m}\right)^{2}}=\$ 37766 \\ &B_{m c s}=B C A C_{\%} 90-B C A C_{d}=\$ 37750 \\ &\text { where } \\ &N=\text { equal quantity of activity } \\ &C_{p}=\text { pessimestic cost of activity } \\ &C_{m}=\text { most likely cost of activity } \\ &B C A C_{d}=\text { deterministic Budget Cost At Completion of project } \\ &B C A C_{\%} 90=\text { Budget Cost At Completion of project with a probability of 90%} \end{aligned}