Question

Deals. | Phone and internet costs. | Call costs

Deal 1. •R2500 for phone •R2 per minute for calls.
•R50 per month for internet
Deal 2. •R250 per months over 24 •R50 free minutes.
Months icluding internet •R2,50 per minute after free minutes used.
and phone.

Deal 3. •R400 per month over 24 •120 free minutes
Month including internet •R1,50 per minute for after free minutes used
And phone
QUESTION
1-determine the fomular that can be used to calculate the total costs per month (excluding the phone for deal 1) for the THREE DEALS.

Answer 1

Let $X$ be those minutes we will use for a month and $n$(1, 2, or 3) is number deal, so the fomula is

$$TotalCost =50 + (n-2)(n-3)[ X*2 ]/2 -$$ $$- (n-1)(n-3)[250 + 2.50max(0, X-24*50)]+$$ $$+(n-1)(n-2)[400+1.50max(0, X-24*120)]/2$$

If Deal 1 $(n=1)$ : $Total_1 =R50 + (n-2)(n-3)[ X*R2 ];$

If Deal 2 $(n=2):Total_2=R50$ $+R250 + R2.50*max(0, X-24*R50)];$

If Deal 3 $(n=3):Total_3=R50+$$R400+R1.50*max(0, X-24*120);$