Farm Profit
1. **State the problem:**
The farm owner has 140 acres of land to plant corn and soybeans. Each acre of corn yields a profit of 370 and requires 2 hours of labor. Each acre of soybeans yields a profit of 290 and requires 1 hour of labor. The total labor available is 320 hours. We want to find how many acres of corn ($x$) and soybeans ($y$) to plant to maximize profit.
2. **Define variables:**
Let $x$ = acres of corn
Let $y$ = acres of soybeans
3. **Write constraints:**
- Land constraint: $$x + y \leq 140$$
- Labor constraint: $$2x + y \leq 320$$
- Non-negativity: $$x \geq 0, y \geq 0$$
4. **Profit function to maximize:**
$$P = 370x + 290y$$
5. **Find corner points of the feasible region:**
- Intersection of land and labor constraints:
Solve system:
$$x + y = 140$$
$$2x + y = 320$$
Subtract first from second:
$$2x + y - (x + y) = 320 - 140 \Rightarrow x = 180$$
Then $$y = 140 - 180 = -40$$ (not feasible since $y \geq 0$)
- Check intercepts:
For land constraint:
$$x=0 \Rightarrow y=140$$
$$y=0 \Rightarrow x=140$$
For labor constraint:
$$x=0 \Rightarrow y=320$$ (not feasible since land max is 140)
$$y=0 \Rightarrow 2x=320 \Rightarrow x=160$$ (not feasible since land max is 140)
6. **Check feasible corner points:**
- $(0,0)$
- $(0,140)$ (land max)
- $(140,0)$ (land max)
- Intersection of labor constraint with $y=0$ is $x=160$ but land max is 140, so max $x=140$
- Intersection of labor constraint with $x=0$ is $y=320$ but land max is 140, so max $y=140$
7. **Check labor constraint at $(140,0)$:**
$$2(140) + 0 = 280 \leq 320$$ feasible
Check labor constraint at $(0,140)$:
$$2(0) + 140 = 140 \leq 320$$ feasible
8. **Check intersection of labor constraint and land constraint at $y=0$ or $x=0$ is outside land limit, so check intersection of labor constraint and land constraint at $y=140 - x$:**
Substitute $y=140 - x$ into labor constraint:
$$2x + (140 - x) \leq 320 \Rightarrow x + 140 \leq 320 \Rightarrow x \leq 180$$
Since land max is 140, $x=140$ is feasible.
9. **Evaluate profit at corner points:**
- At $(0,140)$:
$$P = 370(0) + 290(140) = 40600$$
- At $(140,0)$:
$$P = 370(140) + 290(0) = 51800$$
- At $(100,40)$ (check if feasible):
Check labor:
$$2(100) + 40 = 240 \leq 320$$
Check land:
$$100 + 40 = 140$$
Profit:
$$370(100) + 290(40) = 37000 + 11600 = 48600$$
10. **Maximum profit is at $(140,0)$ with profit 51800.**
**Final answer:**
The farm owner should plant 140 acres of corn and 0 acres of soybeans to yield a maximum profit of 51800.