a$.$ Current productivity per labor dollar if the process requires $4$ employees: $=$ loaves$/$dollar

b$.$ If Charles must increase the total number of work hours to $790$ in order to employ the new oven loading technique and meet the increased demand, then the productivity would be loaves$/$dollar

c$.$ By adding manpower, the percentage increase in productivity is $\%$

d$.$ If Charles instead chooses to purchase a new blender $($while holding labor constant at $640$ hours at $$8$ per hour$),$ then the productivity is loaves$/$dollar

e$.$ By purchasing a new blender $($while holding labor constant at $640$ hours at $$8$ per hour$),$ the percentage increase in productivity is $($comparing the answer in a$.$ to the answer in $d.)$