Billingham could instead purchase the $XC-900,$ which offers even greater capacity. The cost $of$ the $XC-900is$

$$4\mathrm{.}064\mathrm{.}06$

million. The extra capacity would not $be$ useful $in$ the first two years $of$ operation, but would allow for additional sales $in$ years $3-10.$ What level $of$ additional sales $(above$ the

$$10\mathrm{.}2010\mathrm{.}20$

million expected for the $XC-750)$ per year $in$ those years would justify purchasing the larger machine?

The additional sales are