The table below shows (lifetime) peptic ulcer rates (per 100 population), U, for various family incomes, x, as reported by the 1989 National Health Interview Survey.
| Income |
4000 |
6000 |
8000 |
12000 |
16000 |
20000 |
30000 |
45000 |
60000 |
| Ulcer rate |
14.1 |
13.4 |
13.4 |
12.5 |
12.7 |
12.5 |
11.2 |
9.7 |
8.8 |
(a) Find the equation of the regression line.
Ulcer rate, U(x)=____.
(b) Estimate the peptic ulcer rate for an income level of x0= 21000 according to the linear model in part (a).
Ulcer rate, U(x0)=____.