Answer:
(a) The price for a revenue of $18,750 is $239.2.
(b) They sold 710 colonial houses and 2130 ranch houses
Explanation:
(a) If the weekly revenue is defined as
![r=2p^2+400p](https://img.qammunity.org/2020/formulas/mathematics/college/urb3n9igzif3ztp7rwijxexqcbizbtz9vw.png)
then the price must be calculated as:
![r=2p^2+400p=18750\\\\2p^2+400p-18750=0](https://img.qammunity.org/2020/formulas/mathematics/college/tsrnzlxy61676prvf6hu2ffp6w7bymh8z9.png)
The roots of this function are
![x=(-b\pm √(b^2-4ac))/(2a)=(-400 \pm √(400^2-4*2*(-18750)))/(2*2)\\ \\x=(-400 \pm 556.78)/(4)\\ \\x_1=-39.2\\x_2=239.2](https://img.qammunity.org/2020/formulas/mathematics/college/l4uhvdt5rn7p8xtul9ou0p9te2pkyb2wl0.png)
The first root is negative, so it is not a real solution. So the second root is the answer.
The price for a revenue of $18,750 is $239.2.
(b) Last year they sold three times as many ranch models (Hr) as they did colonial models (Hc):
![H_r=3*H_c](https://img.qammunity.org/2020/formulas/mathematics/college/m0bsdnq9tf09tf2qn94mcwy088ukfdbaut.png)
The total amount of houses sold (colonial + ranch) is 2840
![H_c+H_r=2840\\H_c+3*H_c=2840\\4*H_c=2840\\H_c=2840/4=710\\\\H_r = 3*H_c=3*710=2130](https://img.qammunity.org/2020/formulas/mathematics/college/nci0mvfdeonomxnnvxrwc2vx5wr6foyu2c.png)