An economic consultancy models the weekly demand for premium organic coffee ($Q_c$, in thousands of cups) in a metropolitan area using the following demand function:

$$Q_c=120-4P_c+0.05Y-2P_t$$

where $P_c$ is the price of a cup of coffee (in £), $Y$ is the average weekly disposable income of consumers (in £), and $P_t$ is the price of a pastry (in £) sold at accompanying bakeries.

Based on this demand function, which of the following statements is correct?