The percentage p (of total personal consumption) an individual spends on food is approximately
p = 35 s − 0.25 percentage points
Where s is the percentage the individual spends on post-secondary schooling. An individual finds that they are spending
s = 7 + 0.2 t
Percent of their personal consumption on post-secondary schooling, where t is time in months since January 1. Use direct substitution to express the percentage p as a function of time t (do not simplify the expression), and then use the Chain Rule to estimate how fast the percentage the individual spends on food is changing on November 1. Interpret your answer in the context of the situation.
