00:01
This question, a long distance calling plan charge is 99 cents per minute for any call not exceeding 10, 20 minutes in length and 7 cents for each additional minutes.
00:10
So to determine how much a call lasting for 10 and 18 minutes would cost.
00:15
So first of all, the cost function would look like for the first 20 minutes, that will be, let's say t is the total time and for which we have.
00:27
In fact, rather than finding the cost functions, the numbers are pretty much straightforward, what we are going to do is for four minutes, since the call length is less than 20 minutes, so the call charges are just going to be 99 cents or $0 .99 times four.
00:46
Likewise for 10 minutes, that's going to be, since it is less than 20, once again, that's 0 .99 times 10, which is $9 .9.
00:55
And for part c, for 18 minutes, again, we have 0 .99 times 18 because that is less than $18...