Answer:
The answer is below
Explanation:
a) A linear function shows the relationship between variables. A linear equation is in the form: y = mx + b, where m is the rate of change, b is the value of y when x = 0, y is the dependent variable and x is an independent variable.
Let U represent the number of umbrellas and p the price of the umbrella. At $10 the number of umbrella sold is 18000, it can be represented as (10, 18000) i.e. (p, U)
At $16 the number of umbrella sold is 9000, it can be represented as (16, 9000).
The linear function is determined using:
![U-U_1=(U_2-U_1)/(p_2-p_1)(p-p_1)](https://img.qammunity.org/2021/formulas/mathematics/college/lr9j53h9zl311dskz1kgtk2adwfj304xv3.png)
Given (10, 18000) and (16, 9000):
![U-U_1=(U_2-U_1)/(p_2-p_1)(p-p_1)\\\\U-18000=(9000-18000)/(16-10)(p-10)\\\\U-18000=-1500(p-10)\\\\U-18000=-1500p+15000\\\\U=-1500p+15000+18000\\\\U=-1500p+33000\\\\U(p)=-1500p+33000](https://img.qammunity.org/2021/formulas/mathematics/college/u0ztlexvn5hkxqmmwipxixan5rb8xath86.png)
b) At p = $20, The number of umbrella is:
U(20) = -1500(20)+33000
U(20) = 3000 umbrella