The cost to hire a caterer for a party depends on the number of guests attending. If 100 people attend, the cost per person will be $20. For each person less than 100, the cost will increase by $5. Assume that no more than 100 people will attend. Let x represent the number less than 100 who do not attend. For example, if 95 attend, then x = 5.

(a) Write a function N(x) giving the number of guests.

(b) Write a function G(x) giving the cost per guest.

(c) Write a function N(x) # G(x) for the total cost, C(x).

(d) What is the total cost if 80 people attend?