The table below shows (lifetime) peptic ulcer rates (per 100 population), , for various family incomes, , as reported by the 1989 National Health Interview Survey.
| Income | 4000 | 6000 | 8000 | 12000 | 16000 | 20000 | 30000 | 45000 | 60000 |
| Ulcer rate | 13.7 | 13.7 | 12.9 | 12.1 | 12.4 | 11.6 | 10.8 | 9.1 | 7.9 |
(a) Find the equation of the regression line.
Ulcer rate, .
(b) Estimate the peptic ulcer rate for an income level of 22000 according to the linear model in part (a).
Ulcer rate, .
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