A logistics company has been in business for 4 years and wants to develop monthly indices. Monthly inventory quantities for these years are shown in the table below.

a) Develop monthly indices.

b) Estimate next year’s forecast for the months April, July, and December, assuming that the annual inventory quantity will be 1,500 units.

Inventory Quantities (thousands of units)
MONTH YEAR 1 YEAR 2 YEAR 3 YEAR 4 Jan 82 82 82 82 Feb 70 78 84 89 Mar 85 90 82 77 Apr 91 90 90 88 May 90 90 123 119 Jun 89 120 99 99 Jul 100 99 78 89 Aug 89 103 93 100 Sept 86 92 120 86 Oct 80 84 78 84 Nov 75 83 99 80 Dec 78 82 100 82