Originally Posted by

**srk619** can anyone do this question, im really stuck:

Alan, Barbara, Charles and Deborah each have to pick two authors they read.

Alan chooses Robert Ludlum and Colin Dexter, Barbara chooses Colin Dexter

and Jane Austen, Charles chooses dicck Francis, Colin Dexter and Terry Pratchett, and Deborah chooses Jane Austen and Terry Pratchett.

(a) Denoting the set of people by P = {A, B, C, D} where A, B, C and D stand

for Alan, Barbara Charles and Deborah respectively and the set of authors

by A = {L, d, a, f , p}, where l, d, a, f and p stand for Robert Ludlum, Colin

Dexter, Jane Austen, dicck Francis, and Terry Pratchett respectively, give a

relation (i.e. a subset of P x A) which encapsulates the information given

above.

(b) Explain why it is not possible to use a function from P → A or a function

from A → P to give the relationship between people and authors.

(c) Use projection and inverse projection mappings to give an expression for

the names of all the authors chosen by Barbara.

(d) Use projection and inverse projection mappings together with set algebraic

operations to given an expression for all the readers choosing both dicck

Francis and Robert Ludlum.

thank you