Solving for c:
Start with
[tex]P=cw-(1500+2w)[/tex]
add 1500+2w to both sides:
[tex]P+1500+2w=cw[/tex]
Divide both sides by w:
[tex]\dfrac{P+1500+2w}{w}=c[/tex]
Prize to break even:
If they break even, the profit is zero, and since we know that w=800, the cost is
[tex]\dfrac{P+1500+2w}{w}=c \implies c=\dfrac{0+1500+2\cdot 800}{800}=\dfrac{3100}{800}=\dfrac{31}{8}[/tex]
