Analyze the problem in Exercise 5.1 making use of Equation 4.16.

Refer to Exercise 5.1,

Remy spends her weekly income of $30 on chocolate, q₁, and shampoo, q₂. Initially, when the prices are p₁ = $2 = p₂, she buys q₁ = 10 and q₂ = 5. After the prices change to p₁ = $1 and p₂ = $3, she purchases q₁ = 6 and q₂ = 8. Draw her budget lines and choices in a diagram. Use a revealed preference argument to discuss whether or not she is maximizing her utility before and after the price changes?

Equation 4.16,

(p^a_M – p^b_M) (M_a - M_b) ≤ 0.