Build a phone-book utility that allows you to access and modify an alphabetical list of names, addresses and telephone numbers. Use utilities such as awk and sed, to maintain and edit the file of phone-book information. The user (in this case, you) must be able to read, edit, and delete the phone book contents. The permissions for the phone book database must be such that it is inaccessible to anybody other than the user.

A.) generate scaffolding to create database for your application. develop all the entities identified in assignment #2. add any additional that may be identified later. b.) add data validation rules to the models that are appropriate for your application and data. c.) create links for each scaffold in the header section. part 2: application updates [30 points] a.) add two additional views to the "home" controller you created in assignment #1. b.) the two views should be named as “privacy" and "". c.) link the two newly created views in the footer section. hint: you would need to modify the “home" controller definition and create “privacy. html. erb" and “.html. erb" files in appropriate locations.

Write a function balancechemical to balance chemical reactions by solving a linear set of equations. the inputs arguments are: reagents: symbols of reagents in string row array products: symbols of products in string row array elements: elements in the reaction in string row array elcmpreag: elemental composition of reactants in two dimensional numeric array elcmpprdcts: elemental composition of prducts in two dimensional numeric array hint: the first part of the problem is setting up the set of linear equations that should be solve. the second part of the problem is to find the integers from the solution. one way to do this is to mulitiply the rational basis for the nullspace by increasing larger integers until both the left-and right-side integers exist. for example, for the reaction that involves reacting with to produce and : reagents=["ch4", "o2"]; products =["co2", "h2o"]; elements =["c","h", "o"] elcmpreag=[1,4,0;

Why do we mark tlc plates with pencil and not with pen