Quick question...?

Telecom rates for private telephones in 1988 consisted of a quartely rental fee of $35 plus 20c ($0.20) for every local call.

a)construct a cost function that may be used to determine the quartely telephone bill of a household making only local calls.

b) State the domain and range of the function and hence sketch the graph(how would I do this?)

c) How many local calls could the household make for $87

I have attempted a and c. I'm not too confident with my answers though. Could you please help. Thankyou.

a) let N be the number of calls, we can derive for the quarterly cost, C, to be

C= 35 + 0.2N

B) The range is 0 to infinity, when N=0, then C=35, when N= infinity, then C = infinity. The domain is for all real numbers greater than zero. All you need to do to plot the graph is to construct a table of N values in one column and C in another so as

N C
0 35
1 35.2
Etc

You then plot N on the x-axis and C on the y-axis. a Straight line is generated

c) 87= 35 + 0.2N

N= (87-35)/0.2 = 260 calls, so the caller is a chatterbox.

35+.20(n) where n=number of local calls

D:0 - +infinity
R:0 - +infinity

87=35+.20n solve for n
52=.20n
52/.20=n

a) Every quarter there is a $35.00 fee plus $0.20 for each call.

So, for "n" calls, you have 0.20n dollars in charges. On each quarter you tack on the $35, so for each quarter (Q) your total is:

Q = 35 + 0.20n (dollars)


c) Let Q =$87

==> 35 + 0.20n = 87
==> 0.2n = 52
==> n = 260 (calls can be made)

Does this help?

A.)聽 Cost = $(35+0.2*calls)

C.)聽 Calls = ($87 - $35)/$0.2 = 52/0.2 = 260