DSE 2016 Question 6: Dummy variables and functional forms

Consider the following estimated regression relating expenditures on Food ($Y_{i}$) to Income ($X_{i}$): $\hat{Y}_{i}=145+0.3X_{i}-0.1(X_{i}-X_{i}^{*})D_{i}$, where $i$ denotes the individual, $X_{i}^{*}=500$ is a threshold distinguishing low-income from high-income individuals, and $D_{i}=1$ if $X_{i}\ge X^{*}$ and $0$ otherwise. All estimated coefficients are significant at 5% level. Which of the following statements is false?