In a water distribution network, for a given flow rate through the network, the

performance at a given node is measured by the head water pressure. Satisfactory performance at a

node requires that its pressure be between $6$ and $14$ units. Suppose the pressure at node A is a

normal variable with mean value of $10$ units and c$.$o$.$v$.$ of $20\%.$ What is the probability of

satisfactory performance at node A$.($Ans$.$: $0\mathrm{.}9545)$