Question 1686
1. Let C=f(P) = aP+b.
  Since when P =1, C =a+b = 60...(1)
        when P =2, C =2a+b = 30...(2)
      (2)-(1): a = -30, so b= 60-(-30) = 90,
       So, C = -30 P + 90. 

 2. x      -2-1 0 1 2  (*you had typing error.)
   f(x)    -5-2 1 4 7
   Assume f is linear, let f(x) = ax+b,
   f(0) = b = 1,
   f(1) = a + 1= 4, a =3
   So,f(x) = 3x + 1
   Check: f(-1) = -2+1=-2 (OK)
   f(-3) = -6+1=-5 (OK)

 a.  How fast it takes you to get to work as a function of how fast you drive
 Answer: Since the faster you drive, the shorter time it takes you to work,
         So,it is not linear,in fact T = f(V) = distance/V , V: speed.

b.  Probility of getting into a car accident as a function of how fast you drive.
   Answer: The faster you drive, the higher probability of car accident.
          So, it may be a linear function.
c.  Your height as a fuction of age (from age 0 to 100)
  Answer: No,since it is clear that height is not proportional to age.


 Kenny