The following is the firms' order from the one with the most significant elasticity of substitution to the lowest, respectively: Catering businesses, computer programming, assembly line manufacturing.

1. Catering companies have the highest elasticity of substitution because it's easy to navigate between the production factors associated with the companies. The catering firms usually involve the provision of food services, which are flexible. This means that the number of alternatives that can be used is many.
2. Computer programming is second in order because the procedure involved in designing a workable computer program is more flexible compared to assembly line manufacturing.
3. The assembly line manufacturing is the firm with the lowest elasticity of substitution because it uses complex resources that cannot be replaced easily.