Air Raid Inc. designed $20$ air$-$conditioning systems designed for use by astronauts in the International Space Station. All of them were operated for $1,000$ hours at NASA's test facility. Out of all the systems $2$ of them failed during the test. One of them after $200$ hours and the other after $600$ hours.

Given that the Per Unit Failure Rate is $0\mathrm{.}000106383,$ what is the Mean Time Between Failures?

$2,000$ hours

B $5,300$ hours

C $7,400$ hours

D $9,400$ hours

E $,11,500$ hours