Answer:
a.

b.


Step-by-step explanation:
Remember that for any curve
The tangent vector is given by

And the normal vector is given by

a.
For this case, using the chain rule

And also remember that

Therefore

Similarly, using the quotient rule and the chain rule

And also

Therefore

Notice that
1. 
2. 
b.
Simlarly

and

Therefore

Then

and also

And since

First, there was $37.50.
Then, there was a tax of 8%.
Then, there was a tip of 18%.
Since the tip is after the tax, it's not going to affect it, and we can essentially ignore it.
The real question here is just <em>what is 8% of $37.50?</em>
To find the percent of something, first you need to put the percent as a decimal.
8% in decimal form is 0.08 (If you think about it literally, they're both 8 hundredths)
Finally, just multiply the percent in decimal form by the number.
37.50 dollars × 0.08 = 3 dollars.<em />
She would make 3.00 dollars
50(10) - 20(10) = (10)(50 - 20)
500 - 200 = (10 * 30)
300 = 300
(10)(50 - 20) = 30(10)
(10 * 30) = 300
300 = 300