Suppose you have a process that has parallel redundancy with three parallel paths$($similar to Example $4$ on page $666$ in the text$)....$

Path $1($upper path$)---$includes one element with reliability R$1....$R$1=0\mathrm{.}81$

Path $2($middle path$)$ includes two elements in a series with reliability R$2$ and R$3....$R$2=0\mathrm{.}86$ and R$3=0\mathrm{.}70$

Path $3($lower path$)$ includes one element with reliability R$4....$R$4=0\mathrm{.}80$

What is the reliability for the process with parallel redundancy?$($three decimal places please