A system consists $of$ four subassemblies connected $in$ series. The individual subassembly

reliabilities are $as$ follows:

Subassembly $A=0\mathrm{.}98$

Subassembly $B=0\mathrm{.}85$

Subassembly $C=0\mathrm{.}90$

Subassembly $D=0\mathrm{.}88$