Question: What chain of discount stores last operated in 1990 and used Mammoth Mart for their prototype?

Context paragraphs:
G. E. M. Membership Department Stores: G. E. M. Membership Department Stores, also known as G.E.X. or G.E.S., was a chain of discount stores in the United States and Canada.  The chain extended membership to direct and indirect government employees; the name was an acronym for "Government Employees Mart."

Zayre: Zayre was a chain of discount stores that operated in the eastern half of the United States from 1956 to 1990.  The company's headquarters was in Framingham, Massachusetts.  In October 1988, Zayre's parent company, Zayre Corp., sold the stores to the competing Ames Department Stores, Inc. chain, and in June 1989, Zayre Corp. merged with one of its subsidiaries, The TJX Companies, parent company of T.J. Maxx.  A number of stores retained the Zayre name until 1990, by which time all stores were either closed or converted into Ames stores.  (The TJX Companies, which also owns Marshalls, HomeGoods, and Sierra Trading Post, is still in operation as of 2017.)

Gamble-Skogmo: Gamble-Skogmo Inc. was a conglomerate of retail chains and other businesses that was headquartered in St. Louis Park, Minnesota.  Business operated or franchised by Gamble-Skogmo included Gambles hardware and auto supply stores, Woman's World and Mode O'Day clothing stores, J.M. McDonald department stores, Leath Furniture stores, Tempo and Buckeye Mart Discount Stores, Howard's Brandiscount Department Stores, Rasco Variety Stores, Sarco Outlet Stores, Toy World, Rasco-Tempo, Red Owl Grocery, Snyder Drug and the Aldens mail-order company.  In Canada, retail operations consisted of Macleods Hardware, based in Winnipeg, MB, and Stedmans Department Stores, based in Toronto.  Gamble-Skogmo carried a line of home appliances, including radios, televisions, refrigerators, and freezers, under the Coronado brand name.

P.M. Place Stores: P.M. Place Stores, also known as Place's Discount Stores was a Bethany, Missouri-based, employee-owned chain of discount stores in the United States.  The company primarily operated in towns with a population of 1,500 to 4,000 people in Illinois, Iowa, Kansas, and Missouri.

Howard Brothers Discount Stores: Howard Brothers Discount Stores (informally known as Howard Brothers and Howard's) was a chain of discount stores in the Southeastern United States.  The chain was founded in 1959 by Alton Hardy Howard and W. L. "Jack" Howard, a five-term mayor of Monroe, Louisiana.  In 1969, the company became a publicly traded company.

Mammoth Mart: Mammoth Mart was a discount department store chain, located in the northeastern United States, primarily in the New England area.  The chain was founded by Max Coffman and Henry Gornstein in Framingham, Massachusetts in 1956, and was something of a prototype for the large, downscale department store, selling housewares, hardware and clothing in stark, unfussy buildings, usually in suburban shopping center locations.  Other discount department store retailers like K-Mart, Zayre, and Bradlees would subsequently expand on this concept.

King's (defunct discount store): King's Department Stores was a chain of discount stores in the Eastern United States.  The chain started in 1956, in Brockton, Massachusetts.  They expanded to about 190 stores when, in 1978, they purchased the bankrupt Mammoth Mart chain.  Three stores operated in the Buffalo, New York area.  Because of the Mammoth purchase, they filed for Chapter 11 bankruptcy in 1982, and in 1984 Ames Department Stores purchased the chain and converted most of them into Ames stores.

Coop Prix: Coop Prix is a chain of 315 discount stores throughout Norway managed by Coop Norge and owned by local cooperatives.  The chain was created in 1990 for the cooperatives to be able to compete with other discount stores like REMA 1000 and RIMI.

L. S. Ayres: L. S. Ayres and Company was an Indianapolis, Indiana, department store founded in 1872 by Lyman S. Ayres.  Over the years its Indianapolis flagship store, which opened in 1905 and was later enlarged, became known for its women’s fashions, the Tea Room, holiday events and displays, and the basement budget store.  As urban populations shifted to the suburbs, Ayres established branch stores in new shopping centers in several Indiana cities.  Ayres also acquired retail subsidiaries in Springfield, Illinois; Fort Wayne, Indiana; and Louisville, Kentucky.  Ayr-Way, the Ayres discount store subsidiary, became one of the first discount store divisions launched by a traditional store.  By the end of the 1960s Ayres had become a diversified merchandising business with retail department stores, a chain of discount stores, specialty clothing stores, a home furnishings showroom, and a real estate holding company.  A long-time Ayres slogan, "That Ayres Look", promoted the company as a fashion leader and by 1972 it had become the oldest continuous retail slogan in the United States.

Discount store: A discount store is a retail store which sells products at prices that are lower than the typical market value.  A "full-line discount store" or "mass merchandiser" may offer a wide assortment of goods with a focus on price rather than service, display, or wide choice - such as Aldi and Lidl; a "speciality", "single line", or "category killer" discount store may specialize in specific merchandise such as jewelry, electronic equipment, or electrical appliances, relying on bulk purchase and efficient distribution to keep down cost - such as Toys "R" Us and Staples.  Discount stores are not variety stores, which sell goods at a single price-point or multiples thereof (£1, $2, etc.).  Discount stores differ from variety stores in that they sell many name-brand products, and because of the wide price range of the items offered.  Following World War II, a number of retail establishments in the U.S. began to pursue a high-volume, low-profit-margin strategy designed to attract price-conscious consumers.  This strategy has received renewed interest from retailers and customers alike stemming from the Great Recession that began in 2007 that forced buyers to revisit the approach to the products they wanted.

Supporting paragraphs: Mammoth Mart Zayre
Answer: Zayre