Module 8 :
Illustrative Examples

Question 8.3

Mudra Fabricators Ltd (MFL) produces an item required for industrial consumption. The monthly forecast for year 2004 is given below. MFL has a normal production capacity of 2200 units per month and a current inventory of 1000 left as part of inventory in December 2003.

Month Forecast (units)
Jan 1500
Feb 1000
Mar 1900
Apr 2600
May 2800
Jun 3100
July 3200
Aug 3000
Sep 2000
Oct 1000
Nov 1800
Dec 2200
Total 26100

Production cost is Mu 70 per unit, inventory holding cost is Mu 1.4 per month per unit of ending inventory, overtime costs Mu 6.5 additional per unit and there is Mu 5 per unit charge to change the production rate. Cost of under-time (production below full capacity) is Mu 3 per unit. The demand, which is not satisfied, is charged at Mu 9 per unit.

Evaluate the cost of the following two production plans:
a) produce uniformly at full capacity per month
b) produce 1500 units in Jan to Mar, 2800 units in April- Aug, 2200 units in Sep- Nov and 1500 units in Dec.


Answer 8.3

Option (a) : Uniform production of 2200 units per month

Month Demand Cumulative demand Production Cumulative prod availability End-of-month Inventory
= Beginning Inventory + prodn-demand
(1) (2) (3) (4) (5) (6)=(5)-(3)
Jan 1500 1500 2200 1000+2200=3200 1700
Feb 1000 2500 2200 5400 2900
Mar 1900 4400 2200 7600 3200
Apr 2600 7000 2200 9800 2800
May 2800 9800 2200 12000 2200
June 3100 12,900 2200 14200 1300
July 3200 16,100 2200 16400 300
Aug 3000 19,100 2200 18600 0(Lost sales of 500 units)
Sept 2000 21,100 2200 21300 200
Oct 1000 22,100 2200 23500 1400
Nov 1800 23,900 2200 25700 1800
Dec 2200 26,100 2200 27900 1800

Production cost per month = 2200 units x Mu 50 = Mu 154,000
Total production cost Mu 154,000 x 12 months = Mu 1848,000
Total inventory = 1700 +2900 +…. +1800 = 19600 units
Total Inventory cost = 19600 units x Mu 1.4 = Mu 27,440

Total Lost sales cost = 500 units x Mu 90 = Mu 45,000
Total cost of this plan = Mu 1848,000 + Mu 27,440 + Mu 45,000 =Mu 1920,440

Option (b).

Month Demand Cumulative demand Production Cumulative prod availability End-of-month Inventory= Beginning Inventory + prodn-demand
(1) (2) (3) (4) (5) (6)=(5)-(3)
Jan 1500 1500 1500 1000+1500=2500 1000
Feb 1000 2500 1500 4000 1500
Mar 1900 4400 1500 5500 1100
Apr 2600 7000 2800 8300 1300
May 2800 9800 2800 11,100 1300
June 3100 12,900 2800 13,900 1000
July 3200 16,100 2800 16,700 600
Aug 3000 19,100 2800 19,500 400
Sept 2000 21,100 2200 21,700 600
Oct 1000 22,100 2200 23,900 1800
Nov 1800 23,900 2200 26,100 2200
Dec 2200 26,100 1500 27,600 1500


Cost computations under Option (b)


Month Production Prodn cost (in Mu) End-of-month Inventory= Beginning Inventory + prodn-demand Inv cost (in Mu) Capacity change cost (in Mu) @ Mu 5 per unit OvertimeCost@ Mu 6.5 per unit Under time cos@ Mu 3 per unitt
(1) (2) (3) = (2) x Mu 70 (4) (5) = (4) x Mu 1.4 (6) (7) (8)
Jan 1500 105,000 1000 1400     700 x 3 =2100
Feb 1500 105,000 1500 2100     700 x 3 =2100
Mar 1500 105,000 1100 1540     700 x 3 =2100
Apr 2800 196,000 1300 1820 1300*5=6500 600 x 6.5 =x 3900  
May 2800 196,000 1300 1820   600 x 6.5 =x 3900  
Jun 2800 196,000 1000 1400   600 x 6.5 =x 3900  
July 2800 196,000 600 840   600 x 6.5 =x 3900  
Aug 2800 196,000 400 560   600 x 6.5 =x 3900  
Sept 2200 154,000 600 840 600*5=3000    
Oct 2200 154,000 1800 2520      
Nov 2200 154,000 2200 3080      
Dec 1500 105,000 1500 2100 700*5=3500   700 x 3 =2100
Total coats   1862,000   20,020 13,000 19,500 8,400

Total cost of Option B
Mu 1862,000 + Mu 20,020 + Mu 13,000 + Mu 19,500 + Mu 8,400 = Mu 1992, 920

Thus option (a) is cheaper compared to option
(b) by Mu 1992,920 - Mu 1920, 440 = Mu 72, 480 (or by about 3,7 %) .
Prof.S.G.Deshmukh & Prof.Arun Kanda