National Gears has a machining facility specializing in jobs for the two$-$wheeler components market. The job$-$costing system follows two direct$-$cost categories $($direct materials and direct manufacturing labor$)$ and a single indirect$-$cost pool $($manufacturing overhead, allocated using direct labor$-$hours$).$ The indirect cost$-$allocation rate of the prior system were Rs$.115$ per direct manufacturing labor$-$hour used in producing one item.

Recently, a team with members from product design, manufacturing, and accounting used an activity$-$based approach to refine its job$-$costing system. The two direct$-$cost categories were retained. The team decided to replace the single indirect$-$cost pool with five activitycost pools. These five activity$-$cost pools represent five activity areas at the facility, each with its own supervisor and budget responsibility. Pertinent data are as follows:

$\backslash$table$[[$Activities$,$Cost Driver,Cost$-$Allocation Rate$],[$Materials handling,Parts,Rs$.0\mathrm{.}40],[$Lathe work,Turns,$0\mathrm{.}20],[$Milling$,$Machine$-$hours,$20\mathrm{.}00],[$Grinding$,$Parts,$0\mathrm{.}80],[$Testing$,$Units tested,$15\mathrm{.}00]]$

Two representative jobs $($Job AB$41$ and Job AB$81)$ had the following activities

$\backslash$table$[[,$Job AB$41,$Job AB$81],[,,],[$Direct materials cost per job,Rs$\mathrm{.}10,200,$Rs$\mathrm{.}58,700],[$Direct manufacturing labor cost per job,Rs$.750,$Rs$\mathrm{.}11,250],[$Direct manufacturing labor hours per job,$25,375],[$Parts per job,$500,2,000],[$Turns per job,$20,000,60,000],[$Machine hours per job,$150,1,050],[$Units per job,$10,190]]$

Compute the per unit manufacturing costs of each job under the prior job$-$costing system.

Compute the per unit manufacturing costs of each job under the activity$-$based job$-$costing system.

Comment on the reasons for the difference in product costs.