$6.$ Chemical milling is used in an aircraft plant to create pockets in wing sections made of an aluminum alloy. The starting thickness of a work part of interest is $25$ mm$.$ A series of rectangular$-$shaped pockets are to be etched with dimensions $200$ mm by $400$ mm$.$ The pockets will be $17$ mm deep. The corners of each rectangle have a radius $=15$ mm$.$ The etchant is NaOH. Determine metal removal rate in mm$^3/$min$.$ Answer should be in $*$xxxx$\mathrm{.}2*$ format.