The department of water resources is measuring the width of a flood plain, as shown by f(x). The water measurements (x) are taken in 15 foot increments as shown in the table below:

x: 0 | 15 | 30 | 45 | 60 | 75 | 90 | 105 | 120 |
f(x): 0 | 18 | 24 | 30 | 34 | 28 | 32 | 18 | 9 |

Use the indicated method and n = 4 to estimate the limit of f(x) dx with upper bound 120 and lower bound 0.

a. left hand approximation

b. right hand approximation

c. midpoint approximation