$E=\frac{P+O+4M}{6}$

A team is estimating the cost to build a brick wall. The worst case is estimated to cost $$100,$ best case $$70,$ most likely is $$89.$

Calculate the estimated cost.

a$.89\mathrm{.}33$

b$.$ $$86\mathrm{.}33$

c$.$ $$87\mathrm{.}79$

d$.$ $$87\mathrm{.}67$